1211 C OPYRIGHT Ó 2014
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
The Talar Body Prosthesis: Results at Ten to Thirty-six Years of Follow-up Thos Harnroongroj, MD, and Thossart Harnroongroj, MD Investigation performed at the Department of Orthopaedic Surgery, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background: Satisfactory results of implantation of the talar body prosthesis were reported in 1997, although some complications associated with the initial design were noted. The present study evaluated outcomes of treatment with a modified talar body prosthesis. Methods: Of the thirty-six talar body prostheses implanted with use of a transmalleolar surgical approach from 1974 to 2011, thirty-three were available for follow-up at ten to thirty-six years or had failed prior to that time. The indication for implantation had been osteonecrosis in twenty-three patients, a comminuted talar fracture in eight, and a talar body tumor in two. Results: Twenty-eight of the thirty-three prostheses were still in place at the time of final follow-up and five had failed prior to five years. The duration of follow-up was ten to twenty years in eight patients, twenty to thirty years in eleven, and thirty to thirty-six years in nine. The AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot score did not differ significantly among these three groups. Patients over sixty-five years of age with underlying disease that impeded walking ability had lower AOFAS scores. Early prosthesis failure occurred as a result of size mismatch in two patients, tumor recurrence in one, infection in one, and osteonecrosis of the talar head and neck in one. These failures, which occurred at eight to fifty-seven months, were treated with tibiotalar arthrodesis in three patients, prosthesis revision in one, and belowthe-knee amputation in one. Conclusions: Although early prosthesis failure may occur, survival of the talar body prosthesis can provide satisfactory ankle and foot function. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
T
he talar body prosthesis was originally described by Harnroongroj and Vanadurongwan in 19971. The prosthesis has superior, medial, lateral, and inferior surfaces and serves the function of the talocrural and subtalar joints1,2. The initial report by our group in 1997 revealed satisfactory function of the prosthesis for five to fifteen years1. In 2004, Magnan et al. reported on use of a talar body prosthesis for treatment of traumatic loss of the talus3. In 2012, Taniguchi et al. reported on use of a talar body prosthesis made of ceramic material to treat osteonecrosis of the talus4. Several aspects of the talar body prosthesis and the accompanying surgical technique used by our group have undergone
modification from 1974 to 2011. Early prostheses had a 12-mmlong stem with a diameter of 5 mm at the tip and 9 mm at the base; thus, the stem was rather pointed, and it was narrow compared with the talar neck1. The implant interface with the calcaneus consisted of anterior convex and posterior concave curves. The anterior curve was 2 mm above the posterior curve1, which resulted in prosthesis instability on the calcaneus and loaded the stem of the prosthesis. The prosthesis was subsequently modified anteriorly to make the stem 10 mm in length, with a diameter of 9 mm at the tip and 10 mm at the base; in addition, the anterior convex and posterior concave curves of the inferior
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
J Bone Joint Surg Am. 2014;96:1211-8
d
http://dx.doi.org/10.2106/JBJS.M.00377
1212 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014 d
d
d
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
AT
TEN
TO
ä
TABLE I The Twenty-eight Patients Whose Talar Body Prosthesis Survived for Ten to Thirty-six Years
Patient
Sex
Age at Index Operation, Latest Follow-up (yr)
BMI (kg/m2)
Talar Body Damage*
Cement
1
M
24, 60
22.48
Traumatic ON (coronal shear fracture of talar body)
Y
2
F
21, 57
24.65
Traumatic ON (II)
Y
3
M
31, 66
26.49
Traumatic ON (II)
Y
4
M
25, 60
21.72
Comminuted fracture of talar body
Y
5‡
M
48, 70
25.86
Traumatic ON (II)
Y
6
M
21, 54
25.56
Comminuted fracture of talar body
Y
7
M
36, 68
22.86
Traumatic ON (III)
Y
8
F
40, 71
29.78
Traumatic ON (I)
Y
9
M
29, 60
27.43
Traumatic ON (II)
Y
10
M
25, 55
26.96
Traumatic ON (II)
Y
11
M
27, 54
25.21
Traumatic ON (II)
Y
12
M
48, 74
27.87
Traumatic ON (III)
Y
13
M
22, 47
22.41
Comminuted fracture of talar body
Y
14
M
23, 48
25.35
Traumatic ON (II)
Y
15
M
46, 71
25.46
Comminuted fracture of talar body
Y
16
M
22, 44
24.69
Aneurysmal bone cyst
Y
17
M
56, 78
25.53
Idiopathic ON
Y
18
M
25, 46
22.86
Traumatic ON (II)
N
19
M
35, 56
28.73
Traumatic ON (II)
N
20
F
31, 52
24.52
Traumatic ON (III)
N
21
F
47, 66
27.11
Traumatic ON (II)
Y
22
M
32, 51
29.41
Traumatic ON (II)
Y
23
M
26, 43
24.69
Open comminuted fracture of talar body
N
24
F
53, 70
27.30
Traumatic ON (III)
Y
25
F
21, 36
20.90
Open comminuted fracture of talar body
N
26
M
32, 46
22.06
Traumatic ON (II)
N
27
M
53, 65
25.46
Traumatic ON (II)
Y
28
F
16, 26
25.78
Open comminuted fracture of talar body and bone loss
N
*ON = osteonecrosis. The following value in parentheses indicates the Hawkins classification of the fracture responsible. †DM = diabetes mellitus, and HT = hypertension. ‡This patient had twenty-two years of follow-up prior to death and was analyzed in the group with twenty to thirty years of follow-up.
1213 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
d
d
d
AT
TEN
TO
TABLE I (continued) Duration of Follow-up (yr)
Underlying Disease Impeding Walking Ability†
AOFAS
36
76
36
76
35
DM, HT, lumbar spondylosis
72
22
72
33
76
32
Lumbar spondylosis, osteoarthritis both knees
71
31
DM, HT, lumbar spondylosis
70
31
77
30
76
26
71 76
25
76 Lumbar spondylosis, osteoarthritis both knees
22 22
Associated T12 fracture, patient died of myocardial infarction at 70 yr
76 DM, HT, lumbar spondylosis
25
25
Early-type prosthesis, stem perforated into talonavicular joint resulting in anterior ankle pain, revision of prosthesis at 13 yr
70
35
27
Remarks
71
Walked with cane
77 Cervical myelopathy, osteoarthritis both knees
69
Preoperative subchondral bone sclerosis of distal tibia and preservation of tibiotalar joint, walked with cane
21
69
Preoperative subchondral bone sclerosis of distal tibia and preservation of tibiotalar joint, distal advancement of stem, stiff prosthetic ankle
21
78
21 19
79 Lumbar spondylosis, osteoarthritis both knees
19
77
17
79
17
Lumbar spondylosis, osteoarthritis both knees
Distal advancement of stem
71
Associated fracture of tibial shaft and medial malleolus
69
15
79
14
83
12
79
10
66
Associated fracture of medial malleolus
Associated open fracture of right femoral shaft and medial malleolus, compartment syndrome of right leg, 15° equinus of right foot
1214 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014 d
d
d
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
AT
TEN
TO
aspect of the prosthesis were modified to be at the same level (Fig. 1). Additional changes were made when one of the two prostheses with these initial modifications settled into the posterior facet of the calcaneus. The posterior concave curve was consequently modified to be large enough to cover the posterior facet of the calcaneus, and the level of the lateral wing of the posterior concave curve was modified to be 1.5 mm above that of the medial wing. These modifications of the implant interface with the calcaneus provided stable support of the inferior aspect of the prosthesis on the calcaneus and decreased the inferior load on the prosthesis stem as well as prevented early erosion of the posterior facet of the calcaneus (Fig. 1). Materials and Methods
F
rom 1974 to 2011, thirty-six talar body prostheses were inserted to replace the total talar body for the treatment of osteonecrosis, a severely comminuted fracture, or a benign tumor. Talar body prostheses inserted for the treatment of ankle osteoarthritis, a malignant tumor, or an ankle-hindfoot deformity were excluded from the present study. Surgical exposure through the medial malleolus was performed by means 1 of a medial malleolar osteotomy . During the first sixteen procedures, the tibialis posterior tendon was noted to pass across the surgical field and obstruct the insertion of the prosthesis. Thus, Z-lengthening of this tendon was added in the twenty later procedures to achieve wider surgical exposure and facilitate prosthesis insertion. After the prosthesis had been inserted, the osteotomy of the medial malleolus was reduced and fixed without overtensioning of the deltoid ligament. If overtensioning of the deltoid ligament was noted, partial release of the ligament was performed to prevent varus positioning of the prosthesis at the ankle joint. The tibialis posterior tendon was appropriately tensioned and repaired. Clinical assessment included the AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot score, in which 40 points represent pain and 60 points represent ankle-hindfoot function and alignment. Ankle pain at the time of the latest follow-up was also assessed with use of a 10-point numerical pain scale. Prosthesis failures were identified, and the time and cause of the failure were noted. Thirty-three of the thirty-six talar body prosthesis insertions performed from 1974 to 2001 for the stated indications were included in the present study. Twenty-eight of these prostheses had survived for more than ten years, and the remaining five prostheses had failed within five years after the index operation. Demographic data on the patients with prostheses that survived for more than ten years are shown in Table I. The indication for talar body replacement had been traumatic osteonecrosis resulting from a talar neck fracture in nineteen patients, idiopathic osteonecrosis in one, a severely comminuted fracture in seven, and an aneurysmal bone cyst in one. Mild subchondral sclerosis of the distal aspect of the tibia, with preservation of the tibiotalar joint, was noted preoperatively in the patient with idiopathic osteonecrosis and one of the nineteen patients with traumatic osteonecrosis. The mean age (and standard deviation) at the time of the latest follow-up was 56.9 ± 12.3 years (range, twenty-six to seventy-eight years). The mean body mass index (BMI) at the time of the latest follow-up was 25.3 kg/m2 (range, 20.9 to 29.8 kg/m2). Eight patients over sixtyfive years of age had an underlying disease that impeded walking ability. Three had diabetes mellitus, hypertension, and lumbar spondylosis; four had lumbar spondylosis and knee osteoarthritis; and one had cervical myelopathy and osteoarthritis of both knees. All twenty-eight patients had a stable ankle without deformity preoperatively. Demographic data on the five early prosthesis failures are shown in Table II. The indication for talar body replacement had been osteonecrosis in three patients, a severely comminuted fracture in one, and a benign giant cell tumor in one. Outcomes were studied in patients with ten to twenty, twenty to thirty, and thirty to thirty-six years of follow-up. The data were analyzed with use of the Kruskal-Wallis and Mann-Whitney U tests. A p value of 1 mm of tibiotalar joint space. There is periprosthetic heterotopic ossification around the posterolateral aspect of the prosthesis and osseous extension of the anterior and posterior margins of the distal aspect of the tibia.
minutes but had no ankle pain during this time. The patients then needed five to ten minutes of rest before they could resume walking again. Two of these eight patients walked with a cane. The mobility issues were unrelated to the ankle prosthesis. Twenty-six of the twenty-eight patients had a plantigrade foot with no ankle-hindfoot instability, deformity, or appearance of gait abnormality. One patient had a 15° equinus contracture due to compartment syndrome of the leg; he walked with a gait abnormality, which was corrected by a high-heeled shoe. The remaining patient had a stiff prosthetic ankle with 5° of plantar flexion, no dorsiflexion, and marked restriction of subtalar motion. Twenty-seven patients could perform activities of daily living and had not undergone revision of the prosthesis. The remaining (first) patient had anterior ankle pain resulting from perforation of the prosthesis stem into the talonavicular joint, and a revision prosthesis was placed thirteen years postoperatively with good results (Fig. 2). At ten to twenty years of follow-up, the ankles with a talar body prosthesis had a median plantar flexion of 32° (mean, 32°; range, 22° to 38°). Dorsiflexion ranged from 0° to 10°, with mild to moderate restriction of subtalar motion. At twenty to thirty years of follow-up, the median plantar flexion was 29° (mean, 26°; range, 5° to 32°). Dorsiflexion ranged from 0° to 5°, with moderate restriction of subtalar motion. At thirty to thirty-six years of followup, the median plantar flexion was 28° (mean, 25°; range, 10° to 30°). Dorsiflexion was 0°, with moderate to marked restriction of subtalar motion. The decline in the plantar flexion across the three study periods was significant (p = 0.022). Pairwise comparisons showed significant differences between ten to twenty and twenty to thirty years of follow-up (p = 0.040) and between ten to twenty and thirty to thirty-six years of follow-up (p = 0.011). However, there was no significant difference between twenty to thirty and thirty to thirty-six years of follow-up (p = 0.316).
The median AOFAS ankle-hindfoot score of the surviving prostheses was 78 (mean, 75; range, 66 to 83) at ten to twenty years of follow-up, 76 (mean, 74; range, 69 to 79) at twenty to thirty years, and 76 (mean, 74; range, 70 to 77) at thirty to thirty-six years, with no significant difference among the three follow-up durations (p = 0.510). However, the median score was 70.5 (mean, 70; range, 69 to 71) for the eight patients over sixty-five years of age with an underlying disease that impeded walking ability compared with 76 (mean, 76; range, 66 to 83) for the remaining twenty patients; this difference was significant (p = 0.001). One patient died at seventy years of age; at twenty-two years postoperatively, he had had an AOFAS ankle-hindfoot score of 72. On radiographs, twenty-five of the twenty-eight patients had a well-seated prosthesis, without prosthesis tilting or subsidence into the calcaneus. There was some mild narrowing of the tibiotalar joint space (Figs. 2 and 3). Two patients with osteonecrosis of the talar body and preoperative subchondral bone sclerosis at the distal aspect of the tibia had
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
The Talar Body Prosthesis: Results at Ten to Thirty-six Years of Follow-up Thos Harnroongroj, MD, and Thossart Harnroongroj, MD Investigation performed at the Department of Orthopaedic Surgery, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background: Satisfactory results of implantation of the talar body prosthesis were reported in 1997, although some complications associated with the initial design were noted. The present study evaluated outcomes of treatment with a modified talar body prosthesis. Methods: Of the thirty-six talar body prostheses implanted with use of a transmalleolar surgical approach from 1974 to 2011, thirty-three were available for follow-up at ten to thirty-six years or had failed prior to that time. The indication for implantation had been osteonecrosis in twenty-three patients, a comminuted talar fracture in eight, and a talar body tumor in two. Results: Twenty-eight of the thirty-three prostheses were still in place at the time of final follow-up and five had failed prior to five years. The duration of follow-up was ten to twenty years in eight patients, twenty to thirty years in eleven, and thirty to thirty-six years in nine. The AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot score did not differ significantly among these three groups. Patients over sixty-five years of age with underlying disease that impeded walking ability had lower AOFAS scores. Early prosthesis failure occurred as a result of size mismatch in two patients, tumor recurrence in one, infection in one, and osteonecrosis of the talar head and neck in one. These failures, which occurred at eight to fifty-seven months, were treated with tibiotalar arthrodesis in three patients, prosthesis revision in one, and belowthe-knee amputation in one. Conclusions: Although early prosthesis failure may occur, survival of the talar body prosthesis can provide satisfactory ankle and foot function. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
T
he talar body prosthesis was originally described by Harnroongroj and Vanadurongwan in 19971. The prosthesis has superior, medial, lateral, and inferior surfaces and serves the function of the talocrural and subtalar joints1,2. The initial report by our group in 1997 revealed satisfactory function of the prosthesis for five to fifteen years1. In 2004, Magnan et al. reported on use of a talar body prosthesis for treatment of traumatic loss of the talus3. In 2012, Taniguchi et al. reported on use of a talar body prosthesis made of ceramic material to treat osteonecrosis of the talus4. Several aspects of the talar body prosthesis and the accompanying surgical technique used by our group have undergone
modification from 1974 to 2011. Early prostheses had a 12-mmlong stem with a diameter of 5 mm at the tip and 9 mm at the base; thus, the stem was rather pointed, and it was narrow compared with the talar neck1. The implant interface with the calcaneus consisted of anterior convex and posterior concave curves. The anterior curve was 2 mm above the posterior curve1, which resulted in prosthesis instability on the calcaneus and loaded the stem of the prosthesis. The prosthesis was subsequently modified anteriorly to make the stem 10 mm in length, with a diameter of 9 mm at the tip and 10 mm at the base; in addition, the anterior convex and posterior concave curves of the inferior
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
J Bone Joint Surg Am. 2014;96:1211-8
d
http://dx.doi.org/10.2106/JBJS.M.00377
1212 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014 d
d
d
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
AT
TEN
TO
ä
TABLE I The Twenty-eight Patients Whose Talar Body Prosthesis Survived for Ten to Thirty-six Years
Patient
Sex
Age at Index Operation, Latest Follow-up (yr)
BMI (kg/m2)
Talar Body Damage*
Cement
1
M
24, 60
22.48
Traumatic ON (coronal shear fracture of talar body)
Y
2
F
21, 57
24.65
Traumatic ON (II)
Y
3
M
31, 66
26.49
Traumatic ON (II)
Y
4
M
25, 60
21.72
Comminuted fracture of talar body
Y
5‡
M
48, 70
25.86
Traumatic ON (II)
Y
6
M
21, 54
25.56
Comminuted fracture of talar body
Y
7
M
36, 68
22.86
Traumatic ON (III)
Y
8
F
40, 71
29.78
Traumatic ON (I)
Y
9
M
29, 60
27.43
Traumatic ON (II)
Y
10
M
25, 55
26.96
Traumatic ON (II)
Y
11
M
27, 54
25.21
Traumatic ON (II)
Y
12
M
48, 74
27.87
Traumatic ON (III)
Y
13
M
22, 47
22.41
Comminuted fracture of talar body
Y
14
M
23, 48
25.35
Traumatic ON (II)
Y
15
M
46, 71
25.46
Comminuted fracture of talar body
Y
16
M
22, 44
24.69
Aneurysmal bone cyst
Y
17
M
56, 78
25.53
Idiopathic ON
Y
18
M
25, 46
22.86
Traumatic ON (II)
N
19
M
35, 56
28.73
Traumatic ON (II)
N
20
F
31, 52
24.52
Traumatic ON (III)
N
21
F
47, 66
27.11
Traumatic ON (II)
Y
22
M
32, 51
29.41
Traumatic ON (II)
Y
23
M
26, 43
24.69
Open comminuted fracture of talar body
N
24
F
53, 70
27.30
Traumatic ON (III)
Y
25
F
21, 36
20.90
Open comminuted fracture of talar body
N
26
M
32, 46
22.06
Traumatic ON (II)
N
27
M
53, 65
25.46
Traumatic ON (II)
Y
28
F
16, 26
25.78
Open comminuted fracture of talar body and bone loss
N
*ON = osteonecrosis. The following value in parentheses indicates the Hawkins classification of the fracture responsible. †DM = diabetes mellitus, and HT = hypertension. ‡This patient had twenty-two years of follow-up prior to death and was analyzed in the group with twenty to thirty years of follow-up.
1213 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
d
d
d
AT
TEN
TO
TABLE I (continued) Duration of Follow-up (yr)
Underlying Disease Impeding Walking Ability†
AOFAS
36
76
36
76
35
DM, HT, lumbar spondylosis
72
22
72
33
76
32
Lumbar spondylosis, osteoarthritis both knees
71
31
DM, HT, lumbar spondylosis
70
31
77
30
76
26
71 76
25
76 Lumbar spondylosis, osteoarthritis both knees
22 22
Associated T12 fracture, patient died of myocardial infarction at 70 yr
76 DM, HT, lumbar spondylosis
25
25
Early-type prosthesis, stem perforated into talonavicular joint resulting in anterior ankle pain, revision of prosthesis at 13 yr
70
35
27
Remarks
71
Walked with cane
77 Cervical myelopathy, osteoarthritis both knees
69
Preoperative subchondral bone sclerosis of distal tibia and preservation of tibiotalar joint, walked with cane
21
69
Preoperative subchondral bone sclerosis of distal tibia and preservation of tibiotalar joint, distal advancement of stem, stiff prosthetic ankle
21
78
21 19
79 Lumbar spondylosis, osteoarthritis both knees
19
77
17
79
17
Lumbar spondylosis, osteoarthritis both knees
Distal advancement of stem
71
Associated fracture of tibial shaft and medial malleolus
69
15
79
14
83
12
79
10
66
Associated fracture of medial malleolus
Associated open fracture of right femoral shaft and medial malleolus, compartment syndrome of right leg, 15° equinus of right foot
1214 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 96-A N U M B E R 14 J U LY 16, 2 014 d
d
d
T H E T A L A R B O D Y P R O S T H E S I S : R E S U LT S T H I R T Y- S I X Y E A R S O F F O L L O W - U P
AT
TEN
TO
aspect of the prosthesis were modified to be at the same level (Fig. 1). Additional changes were made when one of the two prostheses with these initial modifications settled into the posterior facet of the calcaneus. The posterior concave curve was consequently modified to be large enough to cover the posterior facet of the calcaneus, and the level of the lateral wing of the posterior concave curve was modified to be 1.5 mm above that of the medial wing. These modifications of the implant interface with the calcaneus provided stable support of the inferior aspect of the prosthesis on the calcaneus and decreased the inferior load on the prosthesis stem as well as prevented early erosion of the posterior facet of the calcaneus (Fig. 1). Materials and Methods
F
rom 1974 to 2011, thirty-six talar body prostheses were inserted to replace the total talar body for the treatment of osteonecrosis, a severely comminuted fracture, or a benign tumor. Talar body prostheses inserted for the treatment of ankle osteoarthritis, a malignant tumor, or an ankle-hindfoot deformity were excluded from the present study. Surgical exposure through the medial malleolus was performed by means 1 of a medial malleolar osteotomy . During the first sixteen procedures, the tibialis posterior tendon was noted to pass across the surgical field and obstruct the insertion of the prosthesis. Thus, Z-lengthening of this tendon was added in the twenty later procedures to achieve wider surgical exposure and facilitate prosthesis insertion. After the prosthesis had been inserted, the osteotomy of the medial malleolus was reduced and fixed without overtensioning of the deltoid ligament. If overtensioning of the deltoid ligament was noted, partial release of the ligament was performed to prevent varus positioning of the prosthesis at the ankle joint. The tibialis posterior tendon was appropriately tensioned and repaired. Clinical assessment included the AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot score, in which 40 points represent pain and 60 points represent ankle-hindfoot function and alignment. Ankle pain at the time of the latest follow-up was also assessed with use of a 10-point numerical pain scale. Prosthesis failures were identified, and the time and cause of the failure were noted. Thirty-three of the thirty-six talar body prosthesis insertions performed from 1974 to 2001 for the stated indications were included in the present study. Twenty-eight of these prostheses had survived for more than ten years, and the remaining five prostheses had failed within five years after the index operation. Demographic data on the patients with prostheses that survived for more than ten years are shown in Table I. The indication for talar body replacement had been traumatic osteonecrosis resulting from a talar neck fracture in nineteen patients, idiopathic osteonecrosis in one, a severely comminuted fracture in seven, and an aneurysmal bone cyst in one. Mild subchondral sclerosis of the distal aspect of the tibia, with preservation of the tibiotalar joint, was noted preoperatively in the patient with idiopathic osteonecrosis and one of the nineteen patients with traumatic osteonecrosis. The mean age (and standard deviation) at the time of the latest follow-up was 56.9 ± 12.3 years (range, twenty-six to seventy-eight years). The mean body mass index (BMI) at the time of the latest follow-up was 25.3 kg/m2 (range, 20.9 to 29.8 kg/m2). Eight patients over sixtyfive years of age had an underlying disease that impeded walking ability. Three had diabetes mellitus, hypertension, and lumbar spondylosis; four had lumbar spondylosis and knee osteoarthritis; and one had cervical myelopathy and osteoarthritis of both knees. All twenty-eight patients had a stable ankle without deformity preoperatively. Demographic data on the five early prosthesis failures are shown in Table II. The indication for talar body replacement had been osteonecrosis in three patients, a severely comminuted fracture in one, and a benign giant cell tumor in one. Outcomes were studied in patients with ten to twenty, twenty to thirty, and thirty to thirty-six years of follow-up. The data were analyzed with use of the Kruskal-Wallis and Mann-Whitney U tests. A p value of 1 mm of tibiotalar joint space. There is periprosthetic heterotopic ossification around the posterolateral aspect of the prosthesis and osseous extension of the anterior and posterior margins of the distal aspect of the tibia.
minutes but had no ankle pain during this time. The patients then needed five to ten minutes of rest before they could resume walking again. Two of these eight patients walked with a cane. The mobility issues were unrelated to the ankle prosthesis. Twenty-six of the twenty-eight patients had a plantigrade foot with no ankle-hindfoot instability, deformity, or appearance of gait abnormality. One patient had a 15° equinus contracture due to compartment syndrome of the leg; he walked with a gait abnormality, which was corrected by a high-heeled shoe. The remaining patient had a stiff prosthetic ankle with 5° of plantar flexion, no dorsiflexion, and marked restriction of subtalar motion. Twenty-seven patients could perform activities of daily living and had not undergone revision of the prosthesis. The remaining (first) patient had anterior ankle pain resulting from perforation of the prosthesis stem into the talonavicular joint, and a revision prosthesis was placed thirteen years postoperatively with good results (Fig. 2). At ten to twenty years of follow-up, the ankles with a talar body prosthesis had a median plantar flexion of 32° (mean, 32°; range, 22° to 38°). Dorsiflexion ranged from 0° to 10°, with mild to moderate restriction of subtalar motion. At twenty to thirty years of follow-up, the median plantar flexion was 29° (mean, 26°; range, 5° to 32°). Dorsiflexion ranged from 0° to 5°, with moderate restriction of subtalar motion. At thirty to thirty-six years of followup, the median plantar flexion was 28° (mean, 25°; range, 10° to 30°). Dorsiflexion was 0°, with moderate to marked restriction of subtalar motion. The decline in the plantar flexion across the three study periods was significant (p = 0.022). Pairwise comparisons showed significant differences between ten to twenty and twenty to thirty years of follow-up (p = 0.040) and between ten to twenty and thirty to thirty-six years of follow-up (p = 0.011). However, there was no significant difference between twenty to thirty and thirty to thirty-six years of follow-up (p = 0.316).
The median AOFAS ankle-hindfoot score of the surviving prostheses was 78 (mean, 75; range, 66 to 83) at ten to twenty years of follow-up, 76 (mean, 74; range, 69 to 79) at twenty to thirty years, and 76 (mean, 74; range, 70 to 77) at thirty to thirty-six years, with no significant difference among the three follow-up durations (p = 0.510). However, the median score was 70.5 (mean, 70; range, 69 to 71) for the eight patients over sixty-five years of age with an underlying disease that impeded walking ability compared with 76 (mean, 76; range, 66 to 83) for the remaining twenty patients; this difference was significant (p = 0.001). One patient died at seventy years of age; at twenty-two years postoperatively, he had had an AOFAS ankle-hindfoot score of 72. On radiographs, twenty-five of the twenty-eight patients had a well-seated prosthesis, without prosthesis tilting or subsidence into the calcaneus. There was some mild narrowing of the tibiotalar joint space (Figs. 2 and 3). Two patients with osteonecrosis of the talar body and preoperative subchondral bone sclerosis at the distal aspect of the tibia had
