Management of non-united four-corner fusions

Principles and Evaluation of Bony Unions

Nonunion is a common and costly problem. Unfortunately, there is no widely agreed upon and standardized definition for nonunion. The evaluation of bony union should start with a thorough history and physical examination. The clinician should consider patient-dependent as well as patient-independent characteristics that may influence the rate of healing and evaluate the patient for physical examination findings suggestive of bony union and infection. Radiographs and clinical examination can help confirm a diagnosis of union. When the diagnosis is in doubt, however, advanced imaging modalities as well as laboratory studies can help a surgeon determine when further intervention is necessary.

Factors Associated With Unplanned Reoperation After 4-Corner Arthrodesis: A Study of 478 Wrists

Purpose

The 4-corner arthrodesis (FCA) is a reliable, motion-sparing technique used to treat scapholunate advanced collapse and scaphoid nonunion advanced collapse arthritis, particularly in stage III wrists in which the capitolunate articulation is compromised. Surgical technique and patient-level variables may influence complications following FCA. We sought to evaluate the rate of complications in a large, combined database and manual chart review study.

Methods

Current Procedural Terminology codes were used to search the United States Veteran's Health Administration corporate database to identify wrists treated with FCA over a 24-year period. A retrospective chart review was completed to collect data regarding scapholunate advanced collapse/scaphoid nonunion advanced collapse stage, implant used, the use of a bone graft, smoking status, and comorbidities for all patients undergoing an FCA. A multivariable cox proportional hazards regression was used to assess hazard ratios for reoperation. Incidence rates and the standard error of the mean for reoperation and conversion to total wrist fusion were calculated after grouping patients by 10-year age categories.

Results

A total of 478 wrists underwent FCA during the study period, with a mean follow-up of 63 months. Seventy-three (16%) wrists required reoperation. The most frequent secondary procedures included unplanned implant removal (8.2%), total wrist arthrodesis (4.6%), and revision FCA (1.7%). Positive smoking history increased the risk of reoperation, whereas posterior interosseous nerve neurectomy, arthritis stage, and fixation type did not have a statistically significant association with reoperation. Younger age demonstrated an increased incidence of overall reoperation and wrist fusion.

Conclusions

The most common reason for reoperation after FCA was implant removal. Smoking history is associated with increased rates of reoperation and wrist arthrodesis. Knowledge of these factors may assist with accurately counseling and indicating patients for FCA.

Type of study/level of evidence

Therapeutic III.

Four-Corner Fusion with Locking Dorsal Circular Plate versus Headless Compression Screws: A Clinico-Radiological Comparative Study

Introduction Four-corner fusion is a technique for the treatment of carpal advanced collapse. It consists of scaphoid excision and arthrodesis of the lunate, triquetrum, hamate, and capitate bones. This can be accomplished with different kinds of osteosynthesis. In the first reports of the use of a circular plate, poor outcomes are described, with high rates of non-union, which decreased in later studies, which highlight certain aspects of the surgical technique.

Objective To report our experience with four-corner fusion with the use of a dorsal locking plate (Xpode, Trimed Inc., Santa Clarita, CA, US), and compare it with another traditional fixation method (3.0-mm headless compression screws [HCSs], Synthes, Slothurn, Switzerland), with an emphasis on union, an assessment of the fincitonal outcomes, and the presence of complications.

Material and Methods A comparative study of two prospective series of patients operated on through two fixation techniques for four-corner fusion using autologous bone graft from the iliac crest.

The first group of patients, evaluated between 2010 and 2012, underwent osteosynthesis with 2 HCSs, with a minimum follow up of 18 months. The second group, evaluated between 2011 and 2014, underwent osteosynthesis with a dorsal locking plate, with a minimium foloow up of 12 months. The patients were operated on by four different surgeons in four centers.

The patients were evaluated with radiographs to establish the presence of union and the time it took to occur. In case of doubt, union was confirmed through a computed tomography (CT) scan at 8 weeks postoperatrively. We also assessed the range of motion, the presence of complications, and function through the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire and a grip strength score.

Results We achieved a union rate of 100% in both groups at similar times. In the dorsal locking plate group, we obtained better full range of motion, particularly in wrist extension, which was statistically significant (p = 0.0016), as well as lower DASH scores, which was also statistically significant (p = 0.0066). Complications were only present in two patients in the HCS group.

Conclusion Both techniques are valid and reproducible for the treatment of wrists with scapholunate advanced collapse (SNAC) and scaphoid non-union advanced collapse (SLAC). Based on the outcomes, with the Xpode plate, the patients presented better ranges of motion and DASH scores; therefore it may be an excellent fixation option in the open four-corner fusion surgical technique. The entry point and configuration of the HCS are fundamental variables to analyze.

The union rate of 100% obtained in the present study contrasts with the high rates of non-union reported in the literature published in the early 2000s.

A Failed 4-Corner Arthrodesis Using a Polyether-Ether-Ketone Implant: A Case Report

CASE

A 59-year-old man underwent scaphoidectomy and 4-corner arthrodesis with a polyether-ether-ketone (PEEK) circular plate for scapholunate advanced collapse of the wrist. Five years later, he presented with a symptomatic nonunion and radiocarpal arthritis. Total wrist arthrodesis with a dorsal plate was performed. During revision surgery, considerable synovitis was encountered. Histological evaluation revealed a foreign body response likely secondary to PEEK particles.

CONCLUSION

Use of PEEK implants can result in an adverse local tissue reaction if particles are generated. This is a rare biomaterial-related complication, and surgeons should be aware of this adverse tissue response when using this or other PEEK implants.

Functional Outcomes After Salvage Procedures for Wrist Trauma and Arthritis (Four-Corner Fusion, Proximal Row Carpectomy, Total Wrist Arthroplasty, Total Wrist Fusion, Wrist Denervation): A Review of Literature

Background:

Several salvage procedures for the arthritically destroyed wrist exist. Each of these has advantages as well as disadvantages.

Aims:

The aim of this article is to give practical insights for the clinician on: (1) biomechanical and clinical fundamentals of normal and impaired wrist motion; (2) difficulties in assessment of postoperative outcome between measured motion by the surgeon and self-reported outcome by the patient; (3) indications for each procedure; and (4) differences in functional outcome between partial and complete motion-preserving as well as complete motion-restricting salvage procedures.

Methods:

In trend, Proximal Row Carpectomy (PRC) is slightly superior over four-corner fusion (4CF) in terms of functional outcome, but the methodology-related postoperative motion is decreased for both procedures. Furthermore, PRC is easier to perform, needs lower costs, and has fewer complications than 4CF. Total Wrist Arthroplasty (TWA) has the advantage compared to PRC and 4CF that the preoperative motion values are preserved, but it is limited by decreased load-bearing capacity for the wrist. Total Wrist Fusion (TWF) is associated with a higher load-bearing capacity for the wrist than TWA, but it is limited for carrying out essential activities of daily living. Both PRC and 4CF can be combined primarily by wrist denervation. Wrist denervation alone does not impair the movement of the wrist.

Results and Conclusion:

Salvage procedures for the arthritically destroyed wrist should be detected regarding patients age- and gender-related claims in work and leisure. Not all of them can be successfully re-employed in their original occupations associated with high load-bearing conditions.

Treatment Outcomes of 4-Corner Arthrodesis for Patients With Advanced Carpal Collapse: An Average of 4 Years' Follow-Up Comparing 2 Different Plate Types

PURPOSE

The objective was to investigate the clinical and subjective outcomes of patients after 4-corner arthrodesis (FCA) for scapholunate advanced collapse (SLAC) or scaphoid nonunion advanced collapse (SNAC) and to analyze complications. Furthermore, we compared the long-term results of a first-generation nonlocking plate (Spider) and a plate with a locking screw design (Flower plate).

METHODS

In a retrospective cohort study, we included 39 patients with stage II or III SLAC or SNAC who underwent FCA. Twenty wrists were treated with a nonlocking plate and 19 with a locking plate. Patients completed the Patient-Rated Wrist Evaluation (PRWE) and the Michigan Hand Outcomes Questionnaire (MHQ). Active range of wrist motion, radiological signs such as impingement, and signs of implant loosening and nonunion, as well as postoperative complications, were assessed.

RESULTS

After a median postoperative follow-up time of 4.1 years, the PRWE score was 18 and the total MHQ score 79. Patient-reported and clinical outcomes were similar for the 2 plate types. Wrists fixed with the nonlocking plate had more dorsal impingements and loosening than wrists fixed with a locking plate. One nonunion was noted in the nonlocking plate group, and a single case of implant failure was seen for each plate type. A total of 5 patients with a nonlocking plate incurred postoperative complications that required further medical treatment.

CONCLUSIONS

FCA for patients with stage II or III SLAC or SNAC yields positive clinical and subjective outcomes. Based on the high complication rate following FCA with a nonlocking plate, we no longer use this implant and recommend fixation with a locking screw plate.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Ten-Year Minimum Follow-Up of 4-Corner Fusion for SLAC and SNAC Wrist

BACKGROUND

Scapholunate advanced collapse (SLAC) of the wrist is the most common degenerative condition of the wrist. Four-corner fusion (4CF) is performed as salvage surgery, though there is limited information on its long-term results. We hypothesized that 4CF is a durable surgery with good clinical long-term function.

METHODS

A retrospective chart review of patients undergoing 4CF as well as an interview and recent radiographs were obtained. Patients with a follow-up period of less than 10 years were excluded. Long-term evaluation included standard wrist radiographs, wrist range of motion, and the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire. Radiographs were evaluated and described by the Kellgren-Lawrence classification.

RESULTS

Four hundred eighty-nine wrists underwent a 4CF for SLAC wrist from 1982 to 2003. Twelve patients (15 wrists) were available for follow-up. Average age at surgery was 49.1 years (range, 25-67 years). Average follow-up postsurgery was 18 years (11-27). Scapholunate advanced collapse was the etiology in 13 wrists and scaphoid nonunion advanced collapse in 2 wrists. Average extension/flexion arc was 68.6° (0°-96°), and radial/ulnar deviation arc was 32.9° (0°-5°). QuickDASH scores averaged 7.8 (range, 0-32.5), with only 1 score above 16. Seventy-three percent of radiographs showed minimal to moderate joint destruction, and 27% showed severe joint destruction.

CONCLUSIONS

Scaphoid excision and 4CF remains a reliable procedure for patients with advanced wrist arthritis. Functional results were good at long-term follow-up despite radiographic changes in the radiolunate joint in 73% of patients. Patient satisfaction was high, and functional impairment was low.

Relationship Between Wrist Motion and Capitolunate Reduction in Four-Corner Arthrodesis

The authors retrospectively studied 36 patients with degenerative changes associated with scaphoid nonunion and scapholunate advanced collapse treated with circular plate fixation and bone graft. The goals of the study were to review the incidence of dorsal impingement, nonunion of arthrodesis, loose hardware, broken screws, and limitation in wrist motion associated with correct or incorrect surgical capitolunate reduction. Surgical indications were scapholunate advanced collapse (3 patients), scaphoid nonunion advanced collapse (32 patients), and sequelae of irreducible perilunate dislocation (1 patient). All of the patients were men, with a mean age of 48 years (range, 35-68 years). Average follow-up was 56 months (range, 12-108 months). Functional outcomes evaluated were pain with the visual analog scale, range of motion, grip strength, Disabilities of the Arm, Shoulder and Hand (DASH) score, satisfaction, and time to union. Mean visual analog scale score was 7 (range, 5-9) preoperatively and 1 (range, 0-2) postoperatively. Average wrist range of motion was 42° in extension, 36° in flexion, 15° in ulnar deviation, and 12° in radial deviation. Mean grip strength was 34 kg preoperatively, 50 kg postoperatively, and 56 kg contralaterally. Thirty-five of the 36 patients achieved union at 6 months. Degenerative changes at the radiolunate articulation were present in 1 patient 62 months after surgery, but he was asymptomatic. Mean capitolunate angle was 38º preoperatively and 9º postoperatively. Poor correlation was found between the measured capitate-lunate angle and subsequent flexion and extension (r=0.32 and r=0.17, respectively) using the Pearson correlation coefficient. The authors noted 1 or 2 broken screws in 3 cases (8.3%) and hardware dorsal impingement in the plate in 6 cases (16.6%). Mean DASH score was 24 of 100. Overall patient satisfaction was 70%.

Clinical outcomes of proximal row carpectomy versus four-corner arthrodesis for post-traumatic wrist arthropathy: a systematic review

We conducted a systematic review of studies reporting clinical outcomes after proximal row carpectomy or to four-corner arthrodesis for scaphoid non-union advanced collapse or scapholunate advanced collapse arthritis. Seven studies (Levels I-III; 240 patients, 242 wrists) were evaluated. Significantly different post-operative values were as follows for four-corner arthrodesis versus proximal row carpectomy groups: wrist extension, 39 (SD 11º) versus 43 (SD 11º); wrist flexion, 32 (SD 10º) versus 36 (SD 11º); flexion-extension arc, 62 (SD 14º) versus 75 (SD 10º); radial deviation, 14 (SD 5º) versus 10 (SD 5º); hand grip strength as a percentage of contralateral side, 74% (SD 13) versus 67% (SD 16); overall complication rate, 29% versus 14%. The most common post-operative complications were non-union (grouped incidence, 7%) after four-corner arthrodesis and synovitis and clinically significant oedema (3.1%) after proximal row carpectomy. Radial deviation and post-operative hand grip strength (as a percentage of the contralateral side) were significantly better after four-corner arthrodesis. Four-corner arthrodesis gave significantly greater post-operative radial deviation and grip strength as a percentage of the opposite side. Wrist flexion, extension, and the flexion-extension arc were better after proximal row carpectomy, which also had a lower overall complication rate.

The long-term outcome of four-corner fusion

Introduction Four-corner arthrodesis with excision of the scaphoid is an accepted salvage procedure for scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) and has been performed in our unit for over 20 years. We have undertaken a retrospective review of 116 of these procedures performed in 110 patients between 1992 and 2009. Fifty-eight patients attended for a clinical evaluation, and 29 responded by postal questionnaire. Methods The surgical technique undertaken was standard. That is, through a dorsal approach the scaphoid and tip of the radial styloid were excised. The capitate, lunate, triquetrum, and hamate articular surfaces were then prepared down to bleeding bone. Bone grafts from the scaphoid and radial styloid were then inserted and fixation undertaken. For the latter, various methods were used, including Kirschner (K-)wires, staples, bone screws, but predominantly the Spider plate (Integra Life Sciences, USA). Thereafter the wrist was immobilized for a minimum period of 2 weeks prior to rehabilitation. Results Follow-up was done at a mean of 9 years and 4 months (range 3-19 years). All patients reported a significant improvement in pain relief and ∼50% of flexion extension, although only 40% of radioulnar deviation. Grip strength was again ∼50% of the contralateral side. Most patients reported a significant improvement in function with 87% returning to work. In addition, radiologic evaluation identified 28 patients (31%) who demonstrated ongoing signs of nonunion, particularly around the triquetrum. Fourteen of these (15%) underwent a further procedure, generally with success. Finally, none of the patients demonstrated any arthritic changes in the lunate fossa on follow-up X-ray, and all secondary procedures were undertaken within 2 years of the primary. Discussion This research has demonstrated that four-corner fusion fixed with a circular plate can result in a satisfactory outcome with a reduction in pain, a functional range of motion, and a satisfactory functional outcome. The bulk of the complications appear to occur in the first 2 years after surgery. Thereafter, analysis shows long-term satisfaction with little deterioration. Nonunion, particularly around the triquetrum, continues to be a problem, but it may be that this bone should be excised along with the scaphoid, resulting in a three-part fusion only. Alternatively, a simple capitolunate fusion may be satisfactory.

The use of a pyrocarbon capitate resurfacing implant in chronic wrist disorders

The present study describes the technique and results of proximal row carpectomy with resection of the head of the capitate and replacement with a pyrocarbon capitate resurfacing implant. The major indication for surgical treatment was arthritic changes on the head of the capitate. Patients were assessed by range of motion, grip strength, pain and functional scoring, and radiographic studies. In most patients, wrist function was improved and pain relief was obtained. This surgical procedure may represent a good alternative to total and partial wrist arthrodesis.

OUTCOMES OF FOUR-CORNER ARTHRODESIS USING THE HUBCAPTM CIRCULAR PLATE

We present results of four-corner carpal arthrodesis with the Acumed® HubcapTM circular plate performed at our unit. Eight patients underwent eight procedures over five years, for scapholunate advanced collapse (five wrists) and scaphoid non-union advanced collapse (three wrists). Outcomes included range of motion, quickDASH scores, and visual analogue scores for satisfaction. At final follow-up, mean flexion-extension arc was 56°, mean radial-ulnar deviation 29° and mean quickDASH score was 23/100. Mean score for satisfaction was 7.7/10 (77%). Seven out of eight (87.5%) patients said they would have it done again, and would also recommend it to others. Radiological union was achieved in all cases. One screw broke in one arthrodesis without causing symptoms. The functional outcomes with our use of the HubcapTM are comparable to those reported in literature to date with other circular plates (e.g. Spider plate). There were no non-unions, which is the main reported complication with these plates.

Four-corner arthrodesis concentrator of Ni-Ti memory alloy for carpal collapse

OBJECTIVE

To evaluate the treatment outcomes of a four-corner arthrodesis concentrator of Ni-Ti memory alloy for carpal collapse.

METHODS

From August 2006 to November 2009, 13 patients with carpal collapse underwent scaphoid excision and four-corner (capitate, lunate, triquetrum and hamate) arthrodesis using a four-corner arthrodesis concentrator of Ni-Ti memory alloy. The mean follow-up time was 26.5 months (range, 7-38 months). Various wrist parameters, including the grip strength, range of wrist movements and degree of pain (visual analogue scales) were recorded and compared before and after surgery.

RESULTS

The average fusion time was 2.3 months (range, 2-4 months). Neither non-union nor wound infection was found in any of the patients. By the sixth month postoperatively, the grip strength had reached an average of 32.49 ± 6.21 kg with a range of 22.3-39.7 kg, this being 80.8% of that found on the healthy side. The range of motion reached over 53.0% of that of the healthy side. Preoperatively and at 6 months postoperatively, the mean pain scores were (4.46 ± 1.27) and 1.31 ± 0.95, respectively, when resting (P < 0.05), and 7.00 ± 1.41 and 2.62 ± 1.26, respectively, when weight-bearing (P < 0.05). The mean value of the Krimmer wrist score was 79.2 (range, 64-84). The rate of excellent and fine results was 84.6% (11/13), being excellent in three cases, good in eight and fair in two.

CONCLUSION

Four-corner arthrodesis using a four-corner arthrodesis concentrator of Ni-Ti memory alloy is an effective method for treating carpal collapse and preserving most wrist function.

Pyrocarbon interposition wrist arthroplasty in the treatment of failed wrist procedures

Treatment of failures after prior wrist surgeries with major articular destruction is challenging. In most cases, total wrist fusion is the only possible salvage procedure. We propose a new interposition arthroplasty with a pyrocarbon implant called Amandys. A total of 16 patients, 14 men and 2 women, with a mean age of 56 years were operated on for a failure of wrist surgery performed previously, with an average time lapse of 12 years. The prior surgeries were partial wrist arthrodesis in seven cases, silicone implant interpositions in five cases, advanced Kienböck disease (Lichtman IV) treatment in two cases, proximal row carpectomy in one case, and an isolated scaphoidectomy in one case. A prospective study with clinical and radiological evaluation was performed with a mean follow-up of 24 months (6 to 41 months). Pain and function showed significant improvement. The mean pain score decreased from 7 of 10 to 4 of 10, postoperatively. The mean grip strength was 19 kg (53% of the contralateral side), and the mean range of motion in flexion extension was 68 degrees. Mean strength and range of motion did not change significantly with the operation. The mean QuickDASH (Disability Arm Shoulder and Hand) score decreased from 59 of 100 to 39 of 100. The mean Patient-Rated Wrist Evaluation decreased from 57 of 100 to 33. Two patients (12.5%) required revision for implant repositioning. No dislocation or subsidence of the implant was noted. Pyrocarbon interposition arthroplasty is a new option for treatment of advanced wrist destruction. Preliminary short-term results suggest that it may be a reliable alternative to total wrist fusion. The level of evidence of this study is IV (therapeutic case series).

Results of a method of 4-corner arthrodesis using headless compression screws

PURPOSE

To evaluate the functional and radiographic results of a scaphoid excision and four-corner arthrodesis technique using percutaneous headless compression screws.

METHODS

A cohort of 33 patients, mean age 51 (range, 20-72) years, was treated for scapholunate advanced collapse (19), scaphoid nonunion advanced collapse (12), midcarpal instability (1), and Preiser disease (1). After scaphoid excision and removal of cartilage and subchondral bone in the midcarpal joint through a limited arthrotomy, capitolunate fixation was achieved with a percutaneous, transmetacarpal Acutrak screw (Acumed LLC, Hillsboro, OR), and triquetrohamate fixation was done with a percutaneous screw. Scaphoid was used as a bone graft. The average follow-up time was 8 months (n = 32; range, 6-64 mo).

RESULTS

Union occurred in 31 of 33 wrists (94%). One of the 33 patients had total wrist arthrodesis. Average total active flexion-extension arc was 71° after surgery and 83° before surgery. The postoperative carpal height averaged 0.47 compared to preoperative values of 0.45. The percentage of grip strength significantly improved from 41% before surgery to 80% after surgery. Postoperative mean verbal numerical rating scale pain score was less than 1, statistically better than the preoperative score of 7. Twenty-five of 33 patients were completely pain free. The average postoperative Mayo wrist score was 74, a significant improvement over the preoperative average of 40. Final Disabilities of the Arm, Shoulder, and Hand scores averaged 13 (n = 32; range, 0-49).

CONCLUSIONS

These results were comparable to or better than the results of previously published techniques in terms of fusion rates, alleviation of pain, grip strength, range of motion; Mayo wrist score; and Disabilities of the Arm, Shoulder, and Hand questionnaire score. The technique exploits the theoretical advantages of strong compression between carpals while avoiding a screw-head sized hole in the lunate articular cartilage and preserving the dorsal capsular ligament attachments to the triquetrum.

[Midcarpal fusion using break-away compression screw]

Indication of midcarpal fusion is SNAC or SLAC wrist grade 3. The main complication of circular plate (most common technique) is non-union. In this context, the purpose of our work was to propose the use of break-away compression screws to decrease the rate of non-union. Our series included ten patients. The fusion was fixed using two break-away compression screws (2mm diameter). No bone graft was used. As assessment, subjective (pain, Quick-DASH) and objective (strength, mobility) criteria were reviewed at follow-up. All the criteria were significantly improved after operation except mobility. Among the complications, we noticed one delayed bone-healing with a good outcome and a radiological consolidation. Midcarpal fusion by dorsal approach using break-away compression screws appears to us a technique of interest, not requiring a bone graft, with good cost effectiveness.

Clinical outcome of rearthrodesis in cases of non-union following four-corner fusion

PURPOSE

Four-corner fusion is a proven treatment option for degenerative arthritis of the wrist (SLAC/SNAC); however, in some cases, non-union occurs. The purpose of this study was to evaluate the clinical outcome of rearthrodesis in cases of non-union following four-corner fusion. Furthermore, the goal was to identify the cause of non-union and the location of pseudarthrosis within the fusion.

METHODS

Seven patients (5 males, 2 females) who experienced pseudarthrosis following a four-corner fusion procedure and subsequently elected a rearthrodesis procedure were clinically and radiologically examined. The average age was 58 years (range 48-71 years). Average follow-up after rearthrodesis was 27 months (range 4-60 months). All patients experienced persistent wrist pain and non-union was diagnosed via radiography or CT scan. Range of motion, grip strength, the Modified Mayo Wrist score, and the DASH score were evaluated. The level of pain was determined by using a visual analogue scale. Patients were also asked whether they were satisfied with the procedure and if they would elect it again.

RESULTS

In all patients, the rearthrodesis procedure led to proper bone consolidation, which was verified by radiological examination. Due to persistent wrist pain, one patient required additional procedures (denervation, wrist arthroscopy). In four cases, the location of pseudarthrosis occurred between the triquetrum and hamate. In three cases, the location of pseudoarthrosis was between the capitate and lunate and, additionally, between the triquetrum and hamate. The average DASH score value was 38 and the average Modified Mayo Wrist score was 66. Grip strength was reduced to 85 percent of the contralateral, unaffected side. Three patients indicated that they are dissatisfied with the results and would not elect the procedure again.

CONCLUSIONS

The most frequent location of pseudarthrosis was between the triquetrum and the hamate, which was caused by incomplete cartilage debridement. Proper bone consolidation could be attained by means of rearthrodesis in cases of non-union following four-corner fusion. However, clinical results remain only moderate.