Arch Orthop Trauma Surg (2014) 134:395–404 DOI 10.1007/s00402-013-1913-4
ARTHROSCOPY AND SPORTS MEDICINE
Implant‑free ACL reconstruction: a review Yee Han Dave Lee · Rainer Siebold · Hans H. Paessler
Received: 29 June 2013 / Published online: 31 December 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract Implant-free anterior cruciate ligament (ACL) reconstruction is the fixation of ACL grafts without the need for artificial implants. Our aim was to study the evolution of this technique, review the biomechanical evidence and summarise the results. Implant-free graft fixation for bone patella tendon ACL reconstruction was first described in 1987. This concept of implant-free graft fixation was adapted for hamstring and quadriceps tendons as alternative graft sources. Various biomechanical studies have reported that by adhering to certain technical details, this technique provides comparable fixation strength as conventional ACL fixation. The outcome studies of implant-free ACL reconstruction also report clinical results similar to ACL reconstruction with conventional implants. Keywords Implant-free · Pressfit · ACL reconstruction
Introduction Implant-free anterior cruciate ligament (ACL) reconstruction is the fixation of ACL grafts without the need for artificial implants in the femur, the tibia or both [1–8]. This concept was first described in the 1960s and is intertwined with the history of ACL reconstruction [9]. The use of implants for conventional ACL graft fixation has been associated with problems such as graft injury, Y. H. D. Lee (*) Department of Orthopaedic Surgery, Changi General Hospital, 2, Simei Street 3, Singapore 529889, Republic of Singapore e-mail: [email protected]; [email protected] R. Siebold · H. H. Paessler Centre for Knee, Hip and Foot Surgery, ATOS Klinik Heidelberg, Heidelberg, Germany
implant osteolysis, implant migration and soft tissue irritation. The additional benefits of implant-free ACL surgery are lower costs, improved graft incorporation and ease of revision surgery. Hertel first reported complete implant-free ACL graft fixation in 1987 and this technique has been adopted by various surgeons around the world [3, 4]. Some surgeons have modified this technique to combine implant-free femoral fixation with tibial hardware fixation [1, 10, 11]. Paessler et al. [5–8] adapted this concept of implant-free graft fixation with hamstring and quadriceps tendons as alternative grafts. Various studies have been published on the biomechanical characteristics of implant-free fixation to help understand the performance of this technique [12–19]. With attention to surgical details, this technique provides comparable fixation strength as conventional ACL graft fixation [13–15, 20]. Studies reporting the long-term clinical outcomes of implant-free graft fixation reveal that these techniques provide the same results as conventional techniques using hardware [1, 3, 10, 21–25]. The aim of this article was to review the surgical techniques, surgical modifications, biomechanical data and clinical outcomes of implant-free ACL reconstructions over the last 20 years. It is beneficial to learn about implant-free ACL reconstruction as it helps us better understand the concepts of ACL graft fixation.
Methods Using the PubMed database, a literature search was performed using the term “ACL reconstruction” linked with “implant-free fixation” or “pressfit fixation”. A total of 32 publications were identified with this initial search by the
13
396
Arch Orthop Trauma Surg (2014) 134:395–404
first author. Each publication was reviewed by first author to identify other relevant studies. Studies which met the following inclusion criteria were selected: 1. Studies published between 1991 and 2012. 2. ACL reconstruction with pressfit fixation or implantfree technique. The studies were reviewed by the authors to summarise the surgical techniques, biomechanical data and clinical outcomes published over the last 20 years.
Surgical techniques Bone patella tendon bone pressfit The original bone patella tendon (BTB) pressfit technique described by Hertel et al. [3] was performed arthroscopic-assisted and via a miniarthrotomy. The BTB graft is harvested as a shallow disc (patella end)—25-mm long, 20-mm wide and 5-mm thick with a cylindrical tibia tuberosity bone block (Fig. 1). The tuberosity bone plug is inserted into the femoral tunnel with the bone cortex parallel to the tibial plateau, recreating an anatomic ACL position (Figs. 2, 3). A trough is created above the tibial tunnel exit and the patellar bone disc was driven into the gap for fixation (Fig. 4). Hertel and Behrend [4] later described using bone dowels harvested with hollow reamers to pressfit the BTB graft as tibia fixation. Various other surgeons described modifications to this original technique:
Fig. 1 BTB graft from Hertels original BTB pressfit technique. The medial third of the patella tendon is harvested. The patellar bone block is flat and the tibial bone block is square in crosssection. The tibial bone block is inserted into the femoral tunnel and is 0.5 mm wider than the diameter of the femoral tunnel prepared
13
Fig. 2 BTB pressfit femur technique by Paessler. With the knee flexed to 115°, an impactor is used to impact the cylindrical bone plug (harvested from the tibial tubercle) into the femoral tunnel in such a way that the bone plug cortex is parallel to the tibial plateau. The transverse axis of the graft will coincide with the transverse axis of the previous ACL anatomical attachment
1. Boszatta [26] described a fully arthroscopic technique for BTB implant-free ACL reconstruction. 2. Felmet [27] used bone dowels harvested from the femoral tunnel for additional pressfit fixation in the femur. 3. Gobbi et al. [10] described creating a conical femoral tunnel with an outside-in reamer. The bone graft plug (harvested from tibial side) was wider at the base (13 mm) and 10 mm plug wide at the bone tendon junction. The femoral pressfit was achieved with the graft jammed from outside-into the conical tunnel. 4. Paessler [11] described creating a rectangular slot in the tibia, with a long anteroposterior axis (instead of a round tunnel) to better mimic the ACL insertion.
397
Arch Orthop Trauma Surg (2014) 134:395–404
Fig. 3 BTB femoral pressfit technique. The BTB graft is inserted in flexion. The bone plug—ligament angle in 90° of flexion is 0°. The bone plug ligament angle in extension increases to 75°–90°. In 120° of flexion, this plug lies almost parallel to the tibial plateau
Fig. 5 Paessler’s hamstring pressfit technique with no implants
Fig. 6 Paessler’s hamstring pressfit technique. Picture of the hamstring grafts with the knots (femoral side) and the looped end with the Mersilene tapes passed through (tibial side)
Fig. 4 Original tibial pressfit fixation by Hertel. The tibial trough is deepened and the patellar block is driven into the gap at 30° of knee flexion. The cancellous part of the patellar bone block faces laterally, providing parallel orientation of the fibres of the graft with the knee near extension
5. Paessler and Mastrokalos [5] also modified the patella tendon graft harvest—the standard tibial bone plug was harvested but at the other end, the patella tendon was taken off the periosteum (no bone plug). The patella tendon was whipped stitched and subsequently tied over a tibia bone bridge as tibia fixation. Other authors have described hybrid graft tibia fixation techniques with tibial hardware fixation (using interference
screw [1, 21], post [10] or suture over bone bridge [5–7]) and femoral implant-free fixation. Hamstring and quadriceps tendon pressfit The hamstring implant-free ACL reconstruction was first described by Paessler and Mastrokalos [5]. The semitendinosus and gracilis autografts are folded into half and the ends of each tendon are tied together by a simple knot, creating the femoral end of the graft (Fig. 5). The diameter of the knots was 4 mm more than diameter of the remaining part of the graft (Fig. 6). The gracilis loop must be 10 mm longer because the gracilis tendon knot will be proximal to the semitendinous knot. Two Mersilene tapes are pulled through each of the other looped end of the graft, creating the tibia portion of the graft.
13
398
Fig. 7 Paessler’s hamstring pressfit technique—femoral tunnel preparation. Outside-in reaming till the inner cortex is reached
The femoral tunnel is drilled from within the joint, with a diameter corresponding to the graft size. With a tunnel dilator kept in place 10 mm within the femoral tunnel, the lateral cortex is overdrilled from outside-in (diameter matching the size of the knot) till it reaches the dilator. This creates an outer tunnel for the knot to be seated on the inner notch wall cortical bone (Fig. 7). After the tibial tunnel has been drilled, the graft is passed from the femur side down into the tibia tunnel. The semitendinosus graft is first pulled into the femoral side followed by the thinner gracilis graft. The tibial fixation is achieved by tying the Mersilene tapes across a 1-cm-wide bone bridge distal to the tibial tunnel outlet, at 10° of flexion [5] (Fig. 8). Liu et al. reported a modification of this technique, where the knot was created in the middle of his graft and the ends of the hamstring graft were whipped stitched and
Arch Orthop Trauma Surg (2014) 134:395–404
used for tibia fixation. Additional femoral fixation was achieved by pressfit of the knot in a femoral tunnel, supplemented with a bone dowel. The tibial fixation was achieved with sutures tied over a bone bridge [28]. Paessler described a pressfit technique using a quadriceps tendon graft where a 11-mm-wide and 8-cm-long quadriceps tendon with a 25- to 30-mm-long and 12-mmwide conical patella bone block harvested. The patella bone plug was pressfit in the femoral tunnel and tibial fixation was achieved by tying the sutures over a bone bridge [6]. Prado et al. [62] recently reported a novel technique of double bundle ACL reconstruction with implant-free femoral fixation. The hamstring graft was passed from inside out through the posterolateral femur tunnel and then rerouted from outside-in through the anteromedial femur tunnel, with a portion of the graft siting on the femoral cortex. The tibia end of the graft was fixed with an interference screw.
Biomechanical studies Femoral implant‑free pressfit fixation The initial studies on the biomechanical performance of the femoral pressfit technique were not encouraging [17, 19, 29]. The majority of biomechanical studies evaluated the strength of femoral pressfit fixation. Musahl et al. [29] compared the original pressfit fixation against interference screw fixation, and found that the ultimate load for the pressfit of 215 N was lower than 328 N for the interference screw. Using a porcine tibia model, Rupp et al. [17] also found that pressfit fixation had lower ultimate load to failure of 462.5 N compared to 768.6 N for titanium interference screws and 805.2 N for bioabsorbable screws. Seil et al.
Fig. 8 Paessler’s hamstring pressfit technique—implant-free tibial fixation. A 4.5-mm drill hole is made 1 cm distal to the tibial tunnel and a bone bridge is created. Half the Mersilene tapes are passed under this bone bridge and tied to the other half of the Mersilene tapes
13
399
Arch Orthop Trauma Surg (2014) 134:395–404
used a cyclic loading protocol to simulate early post-surgery rehabilitation and reported that the mean load to failure for titanium screw was 945, 797 N for bioabsorbable screws, and 410–708 N for the pressfit technique. Eighteen out of the 30 pressfit grafts failed by bone plug pull out or plug fracture [19]. The authors concluded that pressfit fixation was not secure enough for accelerated rehabilitation protocol [17, 19]. These initial studies had inferior results as these authors ensure adequate pressfit fixation. Subsequent studies reported that BTB femoral pressfit technique had comparable biomechanical performance to interference screws [14, 20]. Malek et al. [20] reported that pressfit fixation of the bone plug in a tunnel that was undersized by 1 mm showed the same pullout strength as interference screw fixation. Shapiro also reported that circular bone plugs had 19.9 % greater pullout strength than trapezoidal bone plugs [30]. Lee et al. [14] reported that the load to failure results in their biomechanical study for pressfit and interference screw fixation groups were similar. They attributed their improved results to the use of cylindrical bone plugs and the 1.4 mm difference in diameter between the bone plug and tunnel [14]. Two other groups subsequently reported femoral pressfit fixation of BTB grafts (570–1,210 N) gave superior load to failures than interference screw fixation [13, 15]. Various authors have studied the importance of paying attention to technical details as they influenced fixation strength: angle of the femur tunnel, length of the bone block, and tunnel preparation methods [12, 16, 18, 19]. Pavlik et al. [16] demonstrated the importance of angle of the femur tunnel in relation to the loading direction. The ultimate tensile strength was greatest when this angle was 45° (534 N). Seil et al. [19] also found that a higher divergence angle between the loading and tunnel axis gave a higher mean ultimate failure load; the mean load to failure was 410 N at 0°, compared to 708 N at 80°. Studying the influence of bone plug length, SchmidtWiethoff et al. found that the mean load to failure was 236 N for 15 mm plugs and 333 N for 25 mm plugs. They recommended the plug length should be 20–30 mm for adequate pressfit fixation [18]. Dargel et al. [31] also studied the benefits of bone tunnel dilation and found that the group that was underdrilled by 1 mm and dilated up 1 mm gave the highest ultimate failure loads. Kilger et al. [32] studied the hamstring knot pressfit femoral technique and found that the hamstring knot pressfit technique had a load to failure of 540 N and stiffness of 37.8 N/mm. With their robotic universal force moment sensor, the anterior translation with the endobutton fixed grafts and hamstring knot pressfit grafts performed similarly [32]. Both Paessler [7] and Liu et al. [28] in their biomechanical studies reported that the hamstring pressfit technique
had greater pullout strength than BTB grafts fixed with interference screws. Dargel et al. [12] had also studied in cadaver biomechanical model the use of quadriceps tendon for pressfit ACL reconstruction and reported that the failure loads were comparable to BTB grafts. Tibial pressfit fixation Boszatta and Anderl [33] compared the fixation strength of press fit BTB grafts in the tibial tunnel with other fixation methods such as titanium screws, titanium staples and bone bridge suture fixation. For pressfit fixation group, a bone dowel harvested from the tibial tunnel was plugged into the tibial tunnel. The pressfit fixation group had the highest ultimate load to failure of 758 N; compared to interference fixation (572 N), staple (608.4 N) and suture bridge (304.5 N) [33]. Jagodzinski et al. compared the performance of three hamstring tibial graft fixation techniques: a 30-mm interference screw (one size diameter larger than the tibia tunnel), the Mersilene tape was tied over a bone bridge and a whipped stitch hamstring graft tied over a bone bridge. For the second and third groups, a semicircular bone block was inserted for tibial tunnel pressfit fixation. They reported that the tape (second group) had the highest failure loads of 970 N, followed by interference screw (544 N) and suture pressfit (402 N) [34].
Clinical outcome studies Since 2002, 9 studies reviewing the outcomes of a combined total of 867 patients who have undergone pressfit ACL reconstruction have been published. The IKDC objective scores ranged from 77 to 95 % IKDC A or B (normal and nearly normal knees) and the Lysholm scores were between 86 and 93 %. The results of these nine studies are summarised in Table 1 [1, 3, 10, 16, 22, 27, 35, 36, 61].
Discussion The use of implants for ACL graft fixation has simplified ACL reconstruction and made surgical outcomes more predictable, but it is not benign as previously thought. It has been associated with complications such as screw osteolysis, allergic reactions, sterile abscesses, ganglion cysts, fibroxanthoma formation and screw migration [37–44]. There are problems of soft tissue irritation with cortical posts and staples, requiring hardware removal in 21 % of the patients in one series [45]. There is also a risk of graft injury during insertion with metal interference screws [46].
13
13
BTB
BTB
BTB
BTB
Al-Husseiny and Batterjee [1]
Hertel et al. [3]
Pavlik et al. [21]
Felmet [27]
Barie et al. [35]
Age
Femur knot
Femur pressfit Tibia BB
Femur pressfit with dowel
Tibia pressfit
38 (15–58)
148
285
95
42
40
2007–2008 30 (18–45)
106
1998–1999 34.2 (26–64) 25
12.4 (12–14)
8.8
8.8
10.3
35.8 (24–77)
10.7
2.4 (1.83–3.4)
46 months (36–62)
Patient no. Follow-up
1998–1999 29.9 (25–55) 28
1998
1998–2002 29.1
Tibia trough Femur pressfit
Tibia interference screw
1987–1991
1998–2000 26 (21–46)
1994–1995 25
Year
Femur pressfit
Tibia screw/ staple
Femur press fit
Femur conical pressfit Tibia post
Technique
Tibia BB Quad tendon Quad tendon bone block
HS
Wipfler et al. [22] BTB
BTB
Gobbi et al. [10]
Graft
Table 1 Clinical outcomes of implant-free ACL reconstruction
ARTHROSCOPY AND SPORTS MEDICINE
Implant‑free ACL reconstruction: a review Yee Han Dave Lee · Rainer Siebold · Hans H. Paessler
Received: 29 June 2013 / Published online: 31 December 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract Implant-free anterior cruciate ligament (ACL) reconstruction is the fixation of ACL grafts without the need for artificial implants. Our aim was to study the evolution of this technique, review the biomechanical evidence and summarise the results. Implant-free graft fixation for bone patella tendon ACL reconstruction was first described in 1987. This concept of implant-free graft fixation was adapted for hamstring and quadriceps tendons as alternative graft sources. Various biomechanical studies have reported that by adhering to certain technical details, this technique provides comparable fixation strength as conventional ACL fixation. The outcome studies of implant-free ACL reconstruction also report clinical results similar to ACL reconstruction with conventional implants. Keywords Implant-free · Pressfit · ACL reconstruction
Introduction Implant-free anterior cruciate ligament (ACL) reconstruction is the fixation of ACL grafts without the need for artificial implants in the femur, the tibia or both [1–8]. This concept was first described in the 1960s and is intertwined with the history of ACL reconstruction [9]. The use of implants for conventional ACL graft fixation has been associated with problems such as graft injury, Y. H. D. Lee (*) Department of Orthopaedic Surgery, Changi General Hospital, 2, Simei Street 3, Singapore 529889, Republic of Singapore e-mail: [email protected]; [email protected] R. Siebold · H. H. Paessler Centre for Knee, Hip and Foot Surgery, ATOS Klinik Heidelberg, Heidelberg, Germany
implant osteolysis, implant migration and soft tissue irritation. The additional benefits of implant-free ACL surgery are lower costs, improved graft incorporation and ease of revision surgery. Hertel first reported complete implant-free ACL graft fixation in 1987 and this technique has been adopted by various surgeons around the world [3, 4]. Some surgeons have modified this technique to combine implant-free femoral fixation with tibial hardware fixation [1, 10, 11]. Paessler et al. [5–8] adapted this concept of implant-free graft fixation with hamstring and quadriceps tendons as alternative grafts. Various studies have been published on the biomechanical characteristics of implant-free fixation to help understand the performance of this technique [12–19]. With attention to surgical details, this technique provides comparable fixation strength as conventional ACL graft fixation [13–15, 20]. Studies reporting the long-term clinical outcomes of implant-free graft fixation reveal that these techniques provide the same results as conventional techniques using hardware [1, 3, 10, 21–25]. The aim of this article was to review the surgical techniques, surgical modifications, biomechanical data and clinical outcomes of implant-free ACL reconstructions over the last 20 years. It is beneficial to learn about implant-free ACL reconstruction as it helps us better understand the concepts of ACL graft fixation.
Methods Using the PubMed database, a literature search was performed using the term “ACL reconstruction” linked with “implant-free fixation” or “pressfit fixation”. A total of 32 publications were identified with this initial search by the
13
396
Arch Orthop Trauma Surg (2014) 134:395–404
first author. Each publication was reviewed by first author to identify other relevant studies. Studies which met the following inclusion criteria were selected: 1. Studies published between 1991 and 2012. 2. ACL reconstruction with pressfit fixation or implantfree technique. The studies were reviewed by the authors to summarise the surgical techniques, biomechanical data and clinical outcomes published over the last 20 years.
Surgical techniques Bone patella tendon bone pressfit The original bone patella tendon (BTB) pressfit technique described by Hertel et al. [3] was performed arthroscopic-assisted and via a miniarthrotomy. The BTB graft is harvested as a shallow disc (patella end)—25-mm long, 20-mm wide and 5-mm thick with a cylindrical tibia tuberosity bone block (Fig. 1). The tuberosity bone plug is inserted into the femoral tunnel with the bone cortex parallel to the tibial plateau, recreating an anatomic ACL position (Figs. 2, 3). A trough is created above the tibial tunnel exit and the patellar bone disc was driven into the gap for fixation (Fig. 4). Hertel and Behrend [4] later described using bone dowels harvested with hollow reamers to pressfit the BTB graft as tibia fixation. Various other surgeons described modifications to this original technique:
Fig. 1 BTB graft from Hertels original BTB pressfit technique. The medial third of the patella tendon is harvested. The patellar bone block is flat and the tibial bone block is square in crosssection. The tibial bone block is inserted into the femoral tunnel and is 0.5 mm wider than the diameter of the femoral tunnel prepared
13
Fig. 2 BTB pressfit femur technique by Paessler. With the knee flexed to 115°, an impactor is used to impact the cylindrical bone plug (harvested from the tibial tubercle) into the femoral tunnel in such a way that the bone plug cortex is parallel to the tibial plateau. The transverse axis of the graft will coincide with the transverse axis of the previous ACL anatomical attachment
1. Boszatta [26] described a fully arthroscopic technique for BTB implant-free ACL reconstruction. 2. Felmet [27] used bone dowels harvested from the femoral tunnel for additional pressfit fixation in the femur. 3. Gobbi et al. [10] described creating a conical femoral tunnel with an outside-in reamer. The bone graft plug (harvested from tibial side) was wider at the base (13 mm) and 10 mm plug wide at the bone tendon junction. The femoral pressfit was achieved with the graft jammed from outside-into the conical tunnel. 4. Paessler [11] described creating a rectangular slot in the tibia, with a long anteroposterior axis (instead of a round tunnel) to better mimic the ACL insertion.
397
Arch Orthop Trauma Surg (2014) 134:395–404
Fig. 3 BTB femoral pressfit technique. The BTB graft is inserted in flexion. The bone plug—ligament angle in 90° of flexion is 0°. The bone plug ligament angle in extension increases to 75°–90°. In 120° of flexion, this plug lies almost parallel to the tibial plateau
Fig. 5 Paessler’s hamstring pressfit technique with no implants
Fig. 6 Paessler’s hamstring pressfit technique. Picture of the hamstring grafts with the knots (femoral side) and the looped end with the Mersilene tapes passed through (tibial side)
Fig. 4 Original tibial pressfit fixation by Hertel. The tibial trough is deepened and the patellar block is driven into the gap at 30° of knee flexion. The cancellous part of the patellar bone block faces laterally, providing parallel orientation of the fibres of the graft with the knee near extension
5. Paessler and Mastrokalos [5] also modified the patella tendon graft harvest—the standard tibial bone plug was harvested but at the other end, the patella tendon was taken off the periosteum (no bone plug). The patella tendon was whipped stitched and subsequently tied over a tibia bone bridge as tibia fixation. Other authors have described hybrid graft tibia fixation techniques with tibial hardware fixation (using interference
screw [1, 21], post [10] or suture over bone bridge [5–7]) and femoral implant-free fixation. Hamstring and quadriceps tendon pressfit The hamstring implant-free ACL reconstruction was first described by Paessler and Mastrokalos [5]. The semitendinosus and gracilis autografts are folded into half and the ends of each tendon are tied together by a simple knot, creating the femoral end of the graft (Fig. 5). The diameter of the knots was 4 mm more than diameter of the remaining part of the graft (Fig. 6). The gracilis loop must be 10 mm longer because the gracilis tendon knot will be proximal to the semitendinous knot. Two Mersilene tapes are pulled through each of the other looped end of the graft, creating the tibia portion of the graft.
13
398
Fig. 7 Paessler’s hamstring pressfit technique—femoral tunnel preparation. Outside-in reaming till the inner cortex is reached
The femoral tunnel is drilled from within the joint, with a diameter corresponding to the graft size. With a tunnel dilator kept in place 10 mm within the femoral tunnel, the lateral cortex is overdrilled from outside-in (diameter matching the size of the knot) till it reaches the dilator. This creates an outer tunnel for the knot to be seated on the inner notch wall cortical bone (Fig. 7). After the tibial tunnel has been drilled, the graft is passed from the femur side down into the tibia tunnel. The semitendinosus graft is first pulled into the femoral side followed by the thinner gracilis graft. The tibial fixation is achieved by tying the Mersilene tapes across a 1-cm-wide bone bridge distal to the tibial tunnel outlet, at 10° of flexion [5] (Fig. 8). Liu et al. reported a modification of this technique, where the knot was created in the middle of his graft and the ends of the hamstring graft were whipped stitched and
Arch Orthop Trauma Surg (2014) 134:395–404
used for tibia fixation. Additional femoral fixation was achieved by pressfit of the knot in a femoral tunnel, supplemented with a bone dowel. The tibial fixation was achieved with sutures tied over a bone bridge [28]. Paessler described a pressfit technique using a quadriceps tendon graft where a 11-mm-wide and 8-cm-long quadriceps tendon with a 25- to 30-mm-long and 12-mmwide conical patella bone block harvested. The patella bone plug was pressfit in the femoral tunnel and tibial fixation was achieved by tying the sutures over a bone bridge [6]. Prado et al. [62] recently reported a novel technique of double bundle ACL reconstruction with implant-free femoral fixation. The hamstring graft was passed from inside out through the posterolateral femur tunnel and then rerouted from outside-in through the anteromedial femur tunnel, with a portion of the graft siting on the femoral cortex. The tibia end of the graft was fixed with an interference screw.
Biomechanical studies Femoral implant‑free pressfit fixation The initial studies on the biomechanical performance of the femoral pressfit technique were not encouraging [17, 19, 29]. The majority of biomechanical studies evaluated the strength of femoral pressfit fixation. Musahl et al. [29] compared the original pressfit fixation against interference screw fixation, and found that the ultimate load for the pressfit of 215 N was lower than 328 N for the interference screw. Using a porcine tibia model, Rupp et al. [17] also found that pressfit fixation had lower ultimate load to failure of 462.5 N compared to 768.6 N for titanium interference screws and 805.2 N for bioabsorbable screws. Seil et al.
Fig. 8 Paessler’s hamstring pressfit technique—implant-free tibial fixation. A 4.5-mm drill hole is made 1 cm distal to the tibial tunnel and a bone bridge is created. Half the Mersilene tapes are passed under this bone bridge and tied to the other half of the Mersilene tapes
13
399
Arch Orthop Trauma Surg (2014) 134:395–404
used a cyclic loading protocol to simulate early post-surgery rehabilitation and reported that the mean load to failure for titanium screw was 945, 797 N for bioabsorbable screws, and 410–708 N for the pressfit technique. Eighteen out of the 30 pressfit grafts failed by bone plug pull out or plug fracture [19]. The authors concluded that pressfit fixation was not secure enough for accelerated rehabilitation protocol [17, 19]. These initial studies had inferior results as these authors ensure adequate pressfit fixation. Subsequent studies reported that BTB femoral pressfit technique had comparable biomechanical performance to interference screws [14, 20]. Malek et al. [20] reported that pressfit fixation of the bone plug in a tunnel that was undersized by 1 mm showed the same pullout strength as interference screw fixation. Shapiro also reported that circular bone plugs had 19.9 % greater pullout strength than trapezoidal bone plugs [30]. Lee et al. [14] reported that the load to failure results in their biomechanical study for pressfit and interference screw fixation groups were similar. They attributed their improved results to the use of cylindrical bone plugs and the 1.4 mm difference in diameter between the bone plug and tunnel [14]. Two other groups subsequently reported femoral pressfit fixation of BTB grafts (570–1,210 N) gave superior load to failures than interference screw fixation [13, 15]. Various authors have studied the importance of paying attention to technical details as they influenced fixation strength: angle of the femur tunnel, length of the bone block, and tunnel preparation methods [12, 16, 18, 19]. Pavlik et al. [16] demonstrated the importance of angle of the femur tunnel in relation to the loading direction. The ultimate tensile strength was greatest when this angle was 45° (534 N). Seil et al. [19] also found that a higher divergence angle between the loading and tunnel axis gave a higher mean ultimate failure load; the mean load to failure was 410 N at 0°, compared to 708 N at 80°. Studying the influence of bone plug length, SchmidtWiethoff et al. found that the mean load to failure was 236 N for 15 mm plugs and 333 N for 25 mm plugs. They recommended the plug length should be 20–30 mm for adequate pressfit fixation [18]. Dargel et al. [31] also studied the benefits of bone tunnel dilation and found that the group that was underdrilled by 1 mm and dilated up 1 mm gave the highest ultimate failure loads. Kilger et al. [32] studied the hamstring knot pressfit femoral technique and found that the hamstring knot pressfit technique had a load to failure of 540 N and stiffness of 37.8 N/mm. With their robotic universal force moment sensor, the anterior translation with the endobutton fixed grafts and hamstring knot pressfit grafts performed similarly [32]. Both Paessler [7] and Liu et al. [28] in their biomechanical studies reported that the hamstring pressfit technique
had greater pullout strength than BTB grafts fixed with interference screws. Dargel et al. [12] had also studied in cadaver biomechanical model the use of quadriceps tendon for pressfit ACL reconstruction and reported that the failure loads were comparable to BTB grafts. Tibial pressfit fixation Boszatta and Anderl [33] compared the fixation strength of press fit BTB grafts in the tibial tunnel with other fixation methods such as titanium screws, titanium staples and bone bridge suture fixation. For pressfit fixation group, a bone dowel harvested from the tibial tunnel was plugged into the tibial tunnel. The pressfit fixation group had the highest ultimate load to failure of 758 N; compared to interference fixation (572 N), staple (608.4 N) and suture bridge (304.5 N) [33]. Jagodzinski et al. compared the performance of three hamstring tibial graft fixation techniques: a 30-mm interference screw (one size diameter larger than the tibia tunnel), the Mersilene tape was tied over a bone bridge and a whipped stitch hamstring graft tied over a bone bridge. For the second and third groups, a semicircular bone block was inserted for tibial tunnel pressfit fixation. They reported that the tape (second group) had the highest failure loads of 970 N, followed by interference screw (544 N) and suture pressfit (402 N) [34].
Clinical outcome studies Since 2002, 9 studies reviewing the outcomes of a combined total of 867 patients who have undergone pressfit ACL reconstruction have been published. The IKDC objective scores ranged from 77 to 95 % IKDC A or B (normal and nearly normal knees) and the Lysholm scores were between 86 and 93 %. The results of these nine studies are summarised in Table 1 [1, 3, 10, 16, 22, 27, 35, 36, 61].
Discussion The use of implants for ACL graft fixation has simplified ACL reconstruction and made surgical outcomes more predictable, but it is not benign as previously thought. It has been associated with complications such as screw osteolysis, allergic reactions, sterile abscesses, ganglion cysts, fibroxanthoma formation and screw migration [37–44]. There are problems of soft tissue irritation with cortical posts and staples, requiring hardware removal in 21 % of the patients in one series [45]. There is also a risk of graft injury during insertion with metal interference screws [46].
13
13
BTB
BTB
BTB
BTB
Al-Husseiny and Batterjee [1]
Hertel et al. [3]
Pavlik et al. [21]
Felmet [27]
Barie et al. [35]
Age
Femur knot
Femur pressfit Tibia BB
Femur pressfit with dowel
Tibia pressfit
38 (15–58)
148
285
95
42
40
2007–2008 30 (18–45)
106
1998–1999 34.2 (26–64) 25
12.4 (12–14)
8.8
8.8
10.3
35.8 (24–77)
10.7
2.4 (1.83–3.4)
46 months (36–62)
Patient no. Follow-up
1998–1999 29.9 (25–55) 28
1998
1998–2002 29.1
Tibia trough Femur pressfit
Tibia interference screw
1987–1991
1998–2000 26 (21–46)
1994–1995 25
Year
Femur pressfit
Tibia screw/ staple
Femur press fit
Femur conical pressfit Tibia post
Technique
Tibia BB Quad tendon Quad tendon bone block
HS
Wipfler et al. [22] BTB
BTB
Gobbi et al. [10]
Graft
Table 1 Clinical outcomes of implant-free ACL reconstruction
