Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-015-3576-x
KNEE
Treatment of patella baja by a modified Z‑plasty Wierer Guido1,2 · Hoser Christian1 · Herbst Elmar1,3 · Abermann Elisabeth1 · Fink Christian1
Received: 4 November 2014 / Accepted: 5 March 2015 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2015
Abstract Purpose The purpose of this study was to evaluate the efficiency of a modified Z-plasty for patellar tendon lengthening for the treatment of patella baja. Rather than adapting only two tendon reins according to the conventional Z-plasty method, the modified Z-plasty provides four reins to enable multifold overlapping of the tendon tissue. Methods Between 2010 and 2012, a modified Z-plasty procedure was performed in four patients suffering from patella baja. Physical examinations and standardized scoring instruments served as the evaluation measures. Results The median preoperative CD ratio of 0.53 (range 0.43–0.62) was corrected to 1.03 (range 1–1.06) after a median follow-up of 34 months (range 23–41 months). The median preoperative flexion of 108° (range 80–135°) improved to 143° (range 110–145°) compared with the flexion of 145° (range 140–145°) of the unaffected knee. No patients showed any signs of extension lag. The median Lysholm score improved from 49 (range 22–80) to 91 (range 67–95), and the Tegner activity level improved from 2 (range 0–6) to 6 (range 2–6). The median VAS status for pain decreased from an average of 8.5 (range 4–10) to 1 (range 0–2). No complications were observed.
* Fink Christian [email protected]
Conclusion The modified Z-plasty procedure is a valuable technique for the treatment of patella baja, especially if allografts are not available. This procedure allowed for early mobilization and achieved excellent clinical results. Level of evidence IV. Keywords Patella baja · Patella infera · Infrapatellar contracture syndrome · Patellar tendon lengthening · Z-plasty
Introduction Patella baja, also called patella infera, frequently occurs in combination with arthrofibrosis following knee surgery, especially in the context of infrapatellar contracture syndrome (IPCS) [1, 3–9, 12–21, 23–28, 30, 31]. The indication for surgery is commonly recommended to be a Caton–Deschamps (CD) ratio less than or equal to 0.6 [4, 19, 20]. Tibial tuberosity proximalization, patellar tendon lengthening or a combination of both techniques is described in the current literature [4, 6, 19]. However, there is concern regarding restricted post-operative mobilization and recurrent joint stiffness following patellar tendon lengthening [7, 14]. Therefore, a modified Z-plasty procedure with augmentation that allows for immediate unrestricted post-operative motion is described. Additionally, sizeable subcutaneous defects, which occur in the case of a conventional Z-plasty, are prevented.
1
Sportsclinic Austria, Innsbruck, Olympiastraße 39, 6020 Innsbruck, Austria
2
Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria
Materials and methods
Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Strasse 22, 81675 Munich, Germany
Two female and two male patients (four knees), with a median age of 38 years (range 28–45 years), were
3
13
Knee Surg Sports Traumatol Arthrosc
prospectively followed up and operated between 2010 and 2012. All of the patients had a history of previous knee injuries and surgical procedures and presented with anterior knee pain and limited ROM. Each case represents an acquired type of patella baja that was diagnosed via lateral radiographs using the Caton–Deschamps ratio [3]. Patients One patient initially sustained a patellar fracture and subsequent knee infection following implant removal after osteosynthesis. The second patient presented with a “re-patella baja” following arthroscopic lateral release and insufficient patellar tendon lengthening, as described by Dejour [6]. The third patient suffered from patella baja following a combined ACL reconstruction and lateral meniscus repair 2 years prior. Post-operatively, she experienced prolonged restricted extension and limited flexion, which was treated using arthroscopic resection of a cyclops lesion 8 months later. Due to a medial meniscus tear, an arthroscopic partial resection was performed another 5 months later. Although she achieved nearly full ROM 1 month post-operatively, this patient presented with pain, limited knee flexion and restricted patellar mobility 1 year later (i.e. 2 years after the initial trauma). The fourth patient sustained a combined ACL, patellar tendon and lateral meniscus tear, which were initially treated using patellar tendon and lateral meniscus suturing. Eight months after the initial trauma, the patient presented with painful knee flexion, restricted patellar mobility, a positive Lachman test and a positive pivot shift test. Following intense physiotherapy, the patient’s symptoms did not improve. In this case, a medial meniscus repair, ACL reconstruction with an ipsilateral semitendinosus tendon graft and patellar tendon lengthening were performed as a one-stage procedure. Surgical technique Before surgery, the patient’s range of motion (ROM) and patellar mobility were re-evaluated under anaesthesia. The patellar height of the unaffected knee was documented and measured at 90° flexion using fluoroscopy. A tourniquet was placed, with the patient in the supine position. An initial arthroscopy was performed. Thorough arthrolysis, debridement and resection of all fibrotic scar tissue and adhesions followed a general inspection. We also used superolateral portals to specifically address the suprapatellar pouch, if needed. The examination focused on all fibrotic areas and adhesions of the Hoffa fat pad to the anterior tibia and patellar ligament, which was better exposed using the subsequent open approach.
13
Fig. 1 An intraoperative view demonstrates the four resulting reins according to the modified Z-plasty technique. The two superficial reins (black box) are turned over to show the two deeper reins (black star)
Modified Z‑plasty Following arthroscopic arthrolysis, a straight longitudinal skin incision was made from the inferior patellar pole to the centre of the tibial tuberosity. The patellar ligament was prepared, and the medial and lateral borders were defined. Then, the patellar ligament was longitudinally incised from the tip of the patella to the tibial tuberosity in the sagittal direction (Figs. 1, 2). The two resulting reins were separated into a superficial layer and a deeper layer by cutting each rein in the frontal plane. Thereby, the medial superficial rein was detached proximal to the patellar insertion, and the deeper rein was detached distal to the tibial insertion. In an opposite manner, the lateral superficial rein was detached distally, and the deeper rein was detached proximally (Figs. 1, 2). The patella was mobilized, and the remaining fibrotic Hoffa fat pad was excised. If knee flexion or patellar mobility was still restricted, an additional peripatellar tissue release was performed. The full range of motion and the engagement of the patella into the trochlear groove throughout the entire ROM were examined. If necessary, the suprapatellar recess was re-evaluated, and an open release was performed.
Knee Surg Sports Traumatol Arthrosc Fig. 2 A comparison between the conventional [6] and modified Z-plasty techniques is demonstrated. a The diagram shows the incision (red line) of a Z-plasty and its two resulting reins (black and white box). b Regarding a conventional Z-plasty, the amount of overlapping tendon tissue (red line) is limited by lengthening. c The modified Z-plasty provides approximately four times more surface area of tendon tissue overlap (red box) than the conventional Z-plasty. The extra overlap is provided by two superficial (hatched black and white box) and two deeper (grey) tendon reins
To secure a sufficient correction of the patellar tendon length, two parallel holes (2.5 mm) were drilled through the patella and the tibial tuberosity, medially to laterally, and a Nr. 5 FibreWire™ (Arthrex, Inc., Naples, FL) suture was pulled through. The knee was flexed to 90°, and under fluoroscopic control, the FibreWire™ (Arthrex, Inc., Naples, FL) loop was tightened, with the patella at the same height as the contralateral side. The tendon reins were re-approximated with resorbable 3.0 sutures. We emphasized an overlapping tension-free adaption with single sutures along the borders of the tendon reins. Following lavage, the peripatellar and subcutaneous tissues were adapted by covering the FibreWire™ (Arthrex, Inc., Naples, FL) loop. Finally, an intraarticular drain and a subcutaneous drain were placed before skin closure.
adjusted to 90° of flexion, and weight bearing was gradually increased. Full weight bearing and unrestricted range of motion were allowed after 6 weeks.
Post‑operative treatment
Results
The patient was immediately mobilized with partial weight bearing and limited flexion up to 60° for the first 2 postoperative weeks. Thereafter, the hinged knee brace was
The median preoperative CD ratio of 0.53 (range 0.43–0.62) improved to 1.03 (range 1–1.06) at the final follow-up.
Outcome evaluation For clinical and functional evaluation, we used the preoperative and post-operative range of motion, Tegner activity level, Lysholm score and visual analogue pain scale (VAS: 1–10) (Table 1). Additionally, we measured the patellar height and calculated the CD ratio from lateral X-rays at the final follow-up. Patients were also asked whether they would consent to undergo the procedure again. The mean follow-up was 33 months (range 23–41 months).
13
Table 1 Patient data
Knee Surg Sports Traumatol Arthrosc Patient
ROM
CD
Lysholm
Tegner
VAS
Pre
FU
Pre
FU
Pre
FU
Pre
FU
Pre
FU
1 2 3 4
135 80 85 130
145 145 110 140
0.48 0.43 0.58 0.62
1.06 1 1.05 1
66 22 32 80
91 90 67 95
6 0 0 4
6 6 2 6
7 10 10 4
1 0 2 1
Median
108
143
0.53
1.03
49
91
2
6
8.5
1
ROM, range of motion (°); CD, Caton–Deschamps ratio; Lysholm, Lysholm score; Tegner, Tegner activity level; VAS, visual analogue pain scale; pre, preoperative; FU, follow-up
The median preoperative flexion of 108° (range 80–135°) improved to 143° (range 110–145°) compared with the flexion of 145° (range 140–145°) of the unaffected knee. No patients showed any signs of extension lag. The median Lysholm score improved from 49 (range 22–80) to 91 (range 67–95), and the Tegner activity level improved from 2 (range 0–6) to 6 (range 2–6). The median preoperative VAS status for pain changed from 8.5 (range 4–10) to 1 (range 0–2), and all patients reported that they would undergo the procedure again. There were no complications.
Discussion The modified Z-plasty procedure combined with early mobilization was associated with excellent results regarding ROM as well as radiological and subjective outcomes (Table 1). Patella baja is a severe complication of knee surgery [1, 3–9, 12–21, 23–28, 30, 31]. Primary and secondary causes or intrinsic and extrinsic factors have been described in the development of patella baja [17, 18, 30]. Furthermore, an altered femorotibial joint line following total knee arthroplasty has been reported to cause a patella baja [2, 22, 29]. All four patients presented with an acquired type of patella baja and were representative of the most common index traumas described in the literature [3, 4, 9, 12, 17–20]. Several operative techniques have been published, with varying outcomes [2–6, 9, 13, 14, 18, 19, 26, 27]. In et al. [13] used the Ilizarov technique, whereas others [14, 27, 31] described a contralateral patellar tendon autograft or various allografts. However, as the availability of allografts is limited in several countries, patellar tendon lengthening and tibial tuberosity transfer are popular methods. Although tibial tuberosity proximalization is a frequently cited technique [3–5, 9, 18], this method often ignores the nature of the pathology. Caton and Dejour proposed that surgery usually demonstrates good results, with a CD ratio
13
≤0.6 [4, 20]. In contrast, we performed patellar tendon lengthening without tibial tubercle proximalization, even in the case of a patellar tendon length over 2.5 cm. There were no anatomical abnormalities regarding the tibial tubercle in our patients and was therefore no indication for transfer using osteotomy. Furthermore, Shabsin [23] described a patellar tendon length of 2.8–6.3 cm measured with MRI in a healthy population. Therefore, there is no strict guideline regarding whether to perform patellar tendon lengthening. However, there has been concern about joint stiffness following patellar tendon lengthening due to restricted post-operative mobilization [7, 14]. We agree with the findings of Drexler et al. [7], who state that the best prevention of ‘re-baja’ is early range of motion exercise. As shown in a comparison of three tendon-lengthening techniques, the conventional Z-plasty technique enabled significantly greater lengthening than the U–T (modified Baker technique) or V–Y (modified Vulpius technique) plasty techniques [10, 11]. Nevertheless, the initial failure load was significantly lower [10]. Therefore, we used augmentation with a Nr. 5 FibreWire™ (Arthrex, Inc., Naples, FL), which provided adequate support for patellar tendon tissue healing and allowed for immediate post-operative range of motion exercises. An additional advantage of the modified Z-plasty procedure is the approximately four times higher tendon tissue surface area overlap compared with conventional Z-plasty (Fig. 2). Moreover, this procedure prevents gapping of the soft tissues, especially during knee flexion. In the case of a conventional Z-plasty, sizeable subcutaneous defects occur, which are likely to become synovial fistulae and may lead to subsequent joint infection [8]. Splitting the original tendon results in thinner reins, which are not of major concern because patella baja is frequently associated with a thickened patellar tendon. Major limitations of this study include the small number of patients and the absence of control groups due to the rarity of this pathology. In daily practice, the modified Z-plasty is a promising technique for patellar tendon lengthening in case of patella baja.
Knee Surg Sports Traumatol Arthrosc
Conclusion The modified Z-plasty is a valuable technique for the treatment of patella baja, especially if allografts are not available. This procedure allowed for early mobilization and achieved excellent clinical results. Acknowledgments We thank Caroline Hepperger from the OSM Research Foundation for her highly motivated contribution in collecting the clinical data used for this study.
References 1. Ahmad CS, Kwak SD, Ateshian GA, Warden WH, Steadman JR, Mow VC (1998) Effects of patellar tendon adhesion to the anterior tibia on knee mechanics. Am J Sports Med 26(5):715–724 2. Burge JR, Sanchez HB, Wagner RA (2014) Quadriceps and patellar tendon pie-crusting as a treatment for limited flexion in total knee arthroplasty. Am J Orthop 43(4):E83–E88 3. Caton J, Deschamps G, Chambat P, Lerat JL, Dejour H (1982) Patella infera. Apropos of 128 cases. Rev Chir Orthop Reparatrice Appar Mot 68(5):317–325 4. Caton JH (2010) The management of patella infera in current practice. Eur J Orthop Surg Traumatol 20:365–371 5. Caton JH, Dejour D (2010) Tibial tubercle osteotomy in patellofemoral instability and in patellar height abnormality. Int Orthop 34:305–309 6. Dejour D, Levigne C, Dejour H (1995) Postoperative low patella. Treatment by lengthening of the patellar tendon. Rev Chir Orthop Reparatrice Appar Mot 81(4):286–295 7. Drexler M, Dwyer T, Marmor M, Sternheim A, Cameron HU, Cameron JC (2013) The treatment of acquired patella baja with proximalize the tibial tuberosity. Knee Surg Sports Traumatol Arthrosc 21(11):2578–2583 8. Fink C, Hausberger M, Hoser C (2012) Combined anterior cruciate ligament reconstruction with patella tendon lengthening following a complex knee injury. In: Sanchis-Alfonso V, Monllau-Garcia JC (eds) The ACL-deficient knee: a problem solving approach. Springer, London, pp 321–328 9. Freiling D, Galla M, Lobenhoffer P (2006) Die Arthrolyse bei chronischen Beugedefiziten des Kniegelenks. Unfallchirurg 109:285–296 10. Gideroglu K, Akan M, Orhun H, Bozdag E, Gül AE, Akgun E, Akoz T (2009) In vivo comparison of biomechanical, histological, and radiological properties of three techniques for tendon lengthening: an experimental study in rabbits. Scand J Plast Reconstr Surg 43(1):1–7 11. Gideroglu K, Toksoy S, Akan M, Yildirim S, Sümbüloğlu E, Akoz T (2009) In-vitro comparison of the lengthening and biomechanical properties of three tendon lengthening techniques. Scand J Plast Reconstr Surg 20(2):107–113 12. Glinz W (1999) Bewegungseinschraenkung nach Trauma und Operationen am Kniegelenk. Arthroskopie 12:222–232 13. In Y, Kim S-J, Kwon Y-J (2007) Patellar tendon lengthening for patella infera using the Ilizarov technique. J Bone Joint Surg Br 89(3):398–400 14. Mariani PP (1994) A new surgical procedure for the treat ment of patella infera. Knee Surg Sports Traumatol Arthrosc 21(2):238–241
15. McReynolds JG, Meyer MH, Rea JB (2009) Infrapatellar contracture syndrome following ACL reconstruction. JAAPA 22(3):23–24, 26 16. Meyer SA, Brown TD, Pederson DR, Albright JP (1993) The effects of patella infera on patellofemoral contact stress. Trans Orthop Res Soc 18:303 17. Paulos LE, Rosenberg TD, Drawbert J, Manning J, Abbott P (1987) Infrapatellar contracture syndrome. An unrecognized cause of knee stiffness with patella entrapment and patella infera. Am J Sports Med 15(4):331–341 18. Paulos LE, Wnorowski DC, Greenwald AE (1994) Infrapatellar contracture syndrome. Diagnosis, treatment, and long-term followup. Am J Sports Med 22(4):440–449 19. Romero J, Borgeat A, Cartier P (1999) Patella baja. Arthroskopie 12:237–245 20. Saggin PRF, Dejour D (2011) Patella Infera and Patella Alta. In: Sanchis-Alfonso V (ed) Anterior knee pain and patellar instability. Springer, London, pp 443–450 21. Schön SN, Afifi FK, Rasch H, Amsler F, Friederich NF, Arnold MP, Hirschmann MT (2013) Assessment of in vivo loading history of the patellofemoral joint: a study combining patellar position, tilt, alignment and bone SPECT/CT. Knee Surg Sports Traumatol Arthrosc 22(12):3039–3046 22. Seo JG, Moon YW, Kim SM, Park SH, Lee BH, Chang MJ, Jo BC (2014) Prevention of pseudo-patella baja during total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/ s00167-014-3257-1 23. Shabshin N, Schweitzer ME, Morrison WB, Parker L (2004) MRI criteria for patella alta and baja. Skelet Radiol 33(8):445–450 24. Singerman R, Davy DT, Goldberg VM (1994) Effects of patella alta and patella infera on patellofemoral contact forces. J Biomech 27(8):1059–1065 25. Skutek M, Elsner H-A, Slateva K, Mayr H-O, Weig T-G, van Griensven M, Krettek C, Bosch U (2004) Screening for arthrofibrosis after anterior cruciate ligament reconstruction: analysis of association with human leukocyte antigen. Arthroscopy 20(5):469–473 26. Sulaiman AR, Halim AS, Azman WS, Eskandar H (2008) Reconstruction of severe patellar infera syndrome with free vascularised composite tensor fascia lata flap. Singap Med J 49(8):205–207 27. Takai S, Shimazaki N, Yoshino N, Watanabe N, Nakachi N, Kobayashi M, Matsusita T (2009) New technique for knee flexion contracture with patella infera using patellar tendon reconstruction combined with anterior capsular shift: a case report. Arch Orthop Trauma Surg 129:1383–1386 28. van Eijden TM, Kouwenhoven E, Weijs WA (1987) Mechanics of the patellar articulation. Effects of patellar ligament length studied with a mathematical model. Acta Orthop Scand 58(5):560–566 29. Villanueva M, Luna A, Pereiro J, Fahandezh-Saddi H, Villa A (2006) Technical solutions for patella baja and arthrofibrosis after total knee replacement. Rev Esp Cir Traumatol Ortop 50:268–276 30. Wojtys EM, Oakes B, Lindenfeld TN, Bach BR Jr (1997) Patella infera syndrome: an analysis of the patellar tendon pathology. Instr Course Lect 46:241–250 31. Yoo J-H, Chang J-D, Seo Y-J, Baek S-W (2011) Reconstruction of a patellar tendon with Achilles tendon allograft for severe patellar infera—a case report. Knee 18(5):350–353
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KNEE
Treatment of patella baja by a modified Z‑plasty Wierer Guido1,2 · Hoser Christian1 · Herbst Elmar1,3 · Abermann Elisabeth1 · Fink Christian1
Received: 4 November 2014 / Accepted: 5 March 2015 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2015
Abstract Purpose The purpose of this study was to evaluate the efficiency of a modified Z-plasty for patellar tendon lengthening for the treatment of patella baja. Rather than adapting only two tendon reins according to the conventional Z-plasty method, the modified Z-plasty provides four reins to enable multifold overlapping of the tendon tissue. Methods Between 2010 and 2012, a modified Z-plasty procedure was performed in four patients suffering from patella baja. Physical examinations and standardized scoring instruments served as the evaluation measures. Results The median preoperative CD ratio of 0.53 (range 0.43–0.62) was corrected to 1.03 (range 1–1.06) after a median follow-up of 34 months (range 23–41 months). The median preoperative flexion of 108° (range 80–135°) improved to 143° (range 110–145°) compared with the flexion of 145° (range 140–145°) of the unaffected knee. No patients showed any signs of extension lag. The median Lysholm score improved from 49 (range 22–80) to 91 (range 67–95), and the Tegner activity level improved from 2 (range 0–6) to 6 (range 2–6). The median VAS status for pain decreased from an average of 8.5 (range 4–10) to 1 (range 0–2). No complications were observed.
* Fink Christian [email protected]
Conclusion The modified Z-plasty procedure is a valuable technique for the treatment of patella baja, especially if allografts are not available. This procedure allowed for early mobilization and achieved excellent clinical results. Level of evidence IV. Keywords Patella baja · Patella infera · Infrapatellar contracture syndrome · Patellar tendon lengthening · Z-plasty
Introduction Patella baja, also called patella infera, frequently occurs in combination with arthrofibrosis following knee surgery, especially in the context of infrapatellar contracture syndrome (IPCS) [1, 3–9, 12–21, 23–28, 30, 31]. The indication for surgery is commonly recommended to be a Caton–Deschamps (CD) ratio less than or equal to 0.6 [4, 19, 20]. Tibial tuberosity proximalization, patellar tendon lengthening or a combination of both techniques is described in the current literature [4, 6, 19]. However, there is concern regarding restricted post-operative mobilization and recurrent joint stiffness following patellar tendon lengthening [7, 14]. Therefore, a modified Z-plasty procedure with augmentation that allows for immediate unrestricted post-operative motion is described. Additionally, sizeable subcutaneous defects, which occur in the case of a conventional Z-plasty, are prevented.
1
Sportsclinic Austria, Innsbruck, Olympiastraße 39, 6020 Innsbruck, Austria
2
Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria
Materials and methods
Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Strasse 22, 81675 Munich, Germany
Two female and two male patients (four knees), with a median age of 38 years (range 28–45 years), were
3
13
Knee Surg Sports Traumatol Arthrosc
prospectively followed up and operated between 2010 and 2012. All of the patients had a history of previous knee injuries and surgical procedures and presented with anterior knee pain and limited ROM. Each case represents an acquired type of patella baja that was diagnosed via lateral radiographs using the Caton–Deschamps ratio [3]. Patients One patient initially sustained a patellar fracture and subsequent knee infection following implant removal after osteosynthesis. The second patient presented with a “re-patella baja” following arthroscopic lateral release and insufficient patellar tendon lengthening, as described by Dejour [6]. The third patient suffered from patella baja following a combined ACL reconstruction and lateral meniscus repair 2 years prior. Post-operatively, she experienced prolonged restricted extension and limited flexion, which was treated using arthroscopic resection of a cyclops lesion 8 months later. Due to a medial meniscus tear, an arthroscopic partial resection was performed another 5 months later. Although she achieved nearly full ROM 1 month post-operatively, this patient presented with pain, limited knee flexion and restricted patellar mobility 1 year later (i.e. 2 years after the initial trauma). The fourth patient sustained a combined ACL, patellar tendon and lateral meniscus tear, which were initially treated using patellar tendon and lateral meniscus suturing. Eight months after the initial trauma, the patient presented with painful knee flexion, restricted patellar mobility, a positive Lachman test and a positive pivot shift test. Following intense physiotherapy, the patient’s symptoms did not improve. In this case, a medial meniscus repair, ACL reconstruction with an ipsilateral semitendinosus tendon graft and patellar tendon lengthening were performed as a one-stage procedure. Surgical technique Before surgery, the patient’s range of motion (ROM) and patellar mobility were re-evaluated under anaesthesia. The patellar height of the unaffected knee was documented and measured at 90° flexion using fluoroscopy. A tourniquet was placed, with the patient in the supine position. An initial arthroscopy was performed. Thorough arthrolysis, debridement and resection of all fibrotic scar tissue and adhesions followed a general inspection. We also used superolateral portals to specifically address the suprapatellar pouch, if needed. The examination focused on all fibrotic areas and adhesions of the Hoffa fat pad to the anterior tibia and patellar ligament, which was better exposed using the subsequent open approach.
13
Fig. 1 An intraoperative view demonstrates the four resulting reins according to the modified Z-plasty technique. The two superficial reins (black box) are turned over to show the two deeper reins (black star)
Modified Z‑plasty Following arthroscopic arthrolysis, a straight longitudinal skin incision was made from the inferior patellar pole to the centre of the tibial tuberosity. The patellar ligament was prepared, and the medial and lateral borders were defined. Then, the patellar ligament was longitudinally incised from the tip of the patella to the tibial tuberosity in the sagittal direction (Figs. 1, 2). The two resulting reins were separated into a superficial layer and a deeper layer by cutting each rein in the frontal plane. Thereby, the medial superficial rein was detached proximal to the patellar insertion, and the deeper rein was detached distal to the tibial insertion. In an opposite manner, the lateral superficial rein was detached distally, and the deeper rein was detached proximally (Figs. 1, 2). The patella was mobilized, and the remaining fibrotic Hoffa fat pad was excised. If knee flexion or patellar mobility was still restricted, an additional peripatellar tissue release was performed. The full range of motion and the engagement of the patella into the trochlear groove throughout the entire ROM were examined. If necessary, the suprapatellar recess was re-evaluated, and an open release was performed.
Knee Surg Sports Traumatol Arthrosc Fig. 2 A comparison between the conventional [6] and modified Z-plasty techniques is demonstrated. a The diagram shows the incision (red line) of a Z-plasty and its two resulting reins (black and white box). b Regarding a conventional Z-plasty, the amount of overlapping tendon tissue (red line) is limited by lengthening. c The modified Z-plasty provides approximately four times more surface area of tendon tissue overlap (red box) than the conventional Z-plasty. The extra overlap is provided by two superficial (hatched black and white box) and two deeper (grey) tendon reins
To secure a sufficient correction of the patellar tendon length, two parallel holes (2.5 mm) were drilled through the patella and the tibial tuberosity, medially to laterally, and a Nr. 5 FibreWire™ (Arthrex, Inc., Naples, FL) suture was pulled through. The knee was flexed to 90°, and under fluoroscopic control, the FibreWire™ (Arthrex, Inc., Naples, FL) loop was tightened, with the patella at the same height as the contralateral side. The tendon reins were re-approximated with resorbable 3.0 sutures. We emphasized an overlapping tension-free adaption with single sutures along the borders of the tendon reins. Following lavage, the peripatellar and subcutaneous tissues were adapted by covering the FibreWire™ (Arthrex, Inc., Naples, FL) loop. Finally, an intraarticular drain and a subcutaneous drain were placed before skin closure.
adjusted to 90° of flexion, and weight bearing was gradually increased. Full weight bearing and unrestricted range of motion were allowed after 6 weeks.
Post‑operative treatment
Results
The patient was immediately mobilized with partial weight bearing and limited flexion up to 60° for the first 2 postoperative weeks. Thereafter, the hinged knee brace was
The median preoperative CD ratio of 0.53 (range 0.43–0.62) improved to 1.03 (range 1–1.06) at the final follow-up.
Outcome evaluation For clinical and functional evaluation, we used the preoperative and post-operative range of motion, Tegner activity level, Lysholm score and visual analogue pain scale (VAS: 1–10) (Table 1). Additionally, we measured the patellar height and calculated the CD ratio from lateral X-rays at the final follow-up. Patients were also asked whether they would consent to undergo the procedure again. The mean follow-up was 33 months (range 23–41 months).
13
Table 1 Patient data
Knee Surg Sports Traumatol Arthrosc Patient
ROM
CD
Lysholm
Tegner
VAS
Pre
FU
Pre
FU
Pre
FU
Pre
FU
Pre
FU
1 2 3 4
135 80 85 130
145 145 110 140
0.48 0.43 0.58 0.62
1.06 1 1.05 1
66 22 32 80
91 90 67 95
6 0 0 4
6 6 2 6
7 10 10 4
1 0 2 1
Median
108
143
0.53
1.03
49
91
2
6
8.5
1
ROM, range of motion (°); CD, Caton–Deschamps ratio; Lysholm, Lysholm score; Tegner, Tegner activity level; VAS, visual analogue pain scale; pre, preoperative; FU, follow-up
The median preoperative flexion of 108° (range 80–135°) improved to 143° (range 110–145°) compared with the flexion of 145° (range 140–145°) of the unaffected knee. No patients showed any signs of extension lag. The median Lysholm score improved from 49 (range 22–80) to 91 (range 67–95), and the Tegner activity level improved from 2 (range 0–6) to 6 (range 2–6). The median preoperative VAS status for pain changed from 8.5 (range 4–10) to 1 (range 0–2), and all patients reported that they would undergo the procedure again. There were no complications.
Discussion The modified Z-plasty procedure combined with early mobilization was associated with excellent results regarding ROM as well as radiological and subjective outcomes (Table 1). Patella baja is a severe complication of knee surgery [1, 3–9, 12–21, 23–28, 30, 31]. Primary and secondary causes or intrinsic and extrinsic factors have been described in the development of patella baja [17, 18, 30]. Furthermore, an altered femorotibial joint line following total knee arthroplasty has been reported to cause a patella baja [2, 22, 29]. All four patients presented with an acquired type of patella baja and were representative of the most common index traumas described in the literature [3, 4, 9, 12, 17–20]. Several operative techniques have been published, with varying outcomes [2–6, 9, 13, 14, 18, 19, 26, 27]. In et al. [13] used the Ilizarov technique, whereas others [14, 27, 31] described a contralateral patellar tendon autograft or various allografts. However, as the availability of allografts is limited in several countries, patellar tendon lengthening and tibial tuberosity transfer are popular methods. Although tibial tuberosity proximalization is a frequently cited technique [3–5, 9, 18], this method often ignores the nature of the pathology. Caton and Dejour proposed that surgery usually demonstrates good results, with a CD ratio
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≤0.6 [4, 20]. In contrast, we performed patellar tendon lengthening without tibial tubercle proximalization, even in the case of a patellar tendon length over 2.5 cm. There were no anatomical abnormalities regarding the tibial tubercle in our patients and was therefore no indication for transfer using osteotomy. Furthermore, Shabsin [23] described a patellar tendon length of 2.8–6.3 cm measured with MRI in a healthy population. Therefore, there is no strict guideline regarding whether to perform patellar tendon lengthening. However, there has been concern about joint stiffness following patellar tendon lengthening due to restricted post-operative mobilization [7, 14]. We agree with the findings of Drexler et al. [7], who state that the best prevention of ‘re-baja’ is early range of motion exercise. As shown in a comparison of three tendon-lengthening techniques, the conventional Z-plasty technique enabled significantly greater lengthening than the U–T (modified Baker technique) or V–Y (modified Vulpius technique) plasty techniques [10, 11]. Nevertheless, the initial failure load was significantly lower [10]. Therefore, we used augmentation with a Nr. 5 FibreWire™ (Arthrex, Inc., Naples, FL), which provided adequate support for patellar tendon tissue healing and allowed for immediate post-operative range of motion exercises. An additional advantage of the modified Z-plasty procedure is the approximately four times higher tendon tissue surface area overlap compared with conventional Z-plasty (Fig. 2). Moreover, this procedure prevents gapping of the soft tissues, especially during knee flexion. In the case of a conventional Z-plasty, sizeable subcutaneous defects occur, which are likely to become synovial fistulae and may lead to subsequent joint infection [8]. Splitting the original tendon results in thinner reins, which are not of major concern because patella baja is frequently associated with a thickened patellar tendon. Major limitations of this study include the small number of patients and the absence of control groups due to the rarity of this pathology. In daily practice, the modified Z-plasty is a promising technique for patellar tendon lengthening in case of patella baja.
Knee Surg Sports Traumatol Arthrosc
Conclusion The modified Z-plasty is a valuable technique for the treatment of patella baja, especially if allografts are not available. This procedure allowed for early mobilization and achieved excellent clinical results. Acknowledgments We thank Caroline Hepperger from the OSM Research Foundation for her highly motivated contribution in collecting the clinical data used for this study.
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