Pyrocardan Scaphotrapeziotrapezoid Joint Arthroplasty for Isolated Osteoarthritis: Results after a Mean Follow-Up of 5 Years

Abstract

Background  Isolated scaphotrapeziotrapezoid (STT) osteoarthritis (OA) mainly develops in women over 50 years of age in a bilateral manner. Many surgical treatments are available, including distal scaphoid resection with or without interposition, trapeziectomy, and STT arthrodesis. However, there is a controversy about which procedure is the most effective.

Purposes  The purpose of this study was to report the outcomes of the Pyrocardan implant for treating STT isolated OA at a mean follow-up of 5 years.

Patients and Methods  Consecutive patients who underwent STT arthroplasty using the Pyrocardan were reviewed retrospectively by an independent examiner who performed a clinical and radiological evaluation.

Results  The mean follow-up time was 5 years (range 3–8 years). Thirteen patients (76%) were followed for more than 5 years. Between the preoperative assessment and the last follow-up, pain levels decreased significantly. There was no significant difference in the mean Kapandji opposition score. Grip and pinch strengths were 88 and 91% of the contralateral side. The active range of motion in flexion–extension and radioulnar deviation was not significantly different to the contralateral side (119° vs. 121° and 58° vs. 52°, p  > 0.1). Functional scores were improved significantly. No identifiable differences were found in the radioscaphoid, capitolunate, and scapholunate angles before and after surgery. In three cases, the preoperative dorsal intercalated scapholunate instability (DISI) failed to be corrected. In one case, DISI appeared after the procedure. There was one asymptomatic dislocation of the implant. Calcification around the trapezium and/or distal scaphoid was found in four cases. The survival rate of the implant without reoperation was 95%.

Conclusions  In the medium term, Pyrocardan implant is an effective treatment for STT OA as it reduces pain, increases grip strength, and maintains wrist mobility. This is consistent with the results of other published case series using pyrocarbon implants. It provides a high rate of patient satisfaction. Nevertheless, the surgical procedure must be done carefully to avoid STT ligament damage, periarticular calcifications, or dislocation.

Isolated scaphotrapeziotrapezoid (STT) osteoarthritis (OA) mainly develops in women over the age of 50 in a bilateral manner. ¹ According to various studies, ^{2 3} isolated STT OA has a prevalence of 2 to 16%. It is associated with trapeziometacarpal (TM) arthritis in 50 to 90% of cases. ^{4 5} No parallel was found between clinical and radiological findings ^{2 6} but there is a correlation with chondrocalcinosis. ⁷ When all medical treatment options have been exhausted, surgery may be considered. Many surgical procedures are available, including trapeziectomy, distal scaphoid resection with or without interposition, and STT arthrodesis. ^{8 9 10 11 12} Their common objective is to relieve pain and preserve strength and function. However, there is a controversy about which procedure is the most effective.

Pyrocarbon implants have been used in the hand and wrist for several years. ^{8 10 13 14 15 16 17 18} They are well tolerated, have similar mechanical properties to those of cortical bone, and do not wear out. The Pyrocardan implant (Stryker, Wright Medical Tornier, Montbonnot Saint Martin, France) has been proposed as a treatment for TM and STT OA. ^{19 20 21} For the STT joint, the aim of this implant is to maintain the stability of the scaphoid by sparing the ligament attachments but also by preserving physiological kinematics and load transmission. Encouraging functional and radiological outcomes were reported at a short-term follow-up. ¹⁰

The purpose of this study was to report the clinical and radiological outcomes of the Pyrocardan implant for treating isolated STT OA in the medium term.

Methods

Patients

In a retrospective study, we reviewed 17 consecutive patients (13 women, 4 men) with a mean age of 68 years (range, 46–79 years) who underwent Pyrocardan STT arthroplasty between 2012 and 2018, with no patients lost to follow-up. One patient was operated on both sides (18 wrists evaluated). All patients had painful advanced isolated STT joint OA that did not respond to conservative treatment. The dominant side was involved in eight cases. None had previously undergone wrist surgery. All patients were treated in the same hand surgery unit by the same hand surgeon with level 5 experience according to Tang and Giddins. ²² This study was approved by our institutional review board. After obtaining their consent, patients were reviewed retrospectively by an independent examiner (level 2) ²² who performed a clinical and radiographical evaluation.

Surgical Procedure and Postoperative Protocol

The surgical procedure has been previously described by Gauthier et al. ¹⁰ The same surgeon performed all the surgeries with the patients under regional anesthesia and a tourniquet applied on the patients' upper arm. An anterior curved incision was made and delimited by the flexor carpi radialis (FCR) tendon, and the volar tubercules of the scaphoid and trapezium. The FCR sheath was opened to release the tendon, to remove any tenosynovitis or synovial cysts, and to trim any torn tendon ends. The STT joint was then opened longitudinally. Bone preparation was performed using a thin oscillating saw and a reamer. The aim was to remodel the concave trapeziotrapezoid surface to impart a slightly anteroposterior and mediolateral convexity. During this preparation, we made sure to spare the articular surface of the scaphoid and the ligament insertions of its distal pole by placing axial traction on the thumb. The FCR tendon was spared by retracting it ulnarly. The trial implant was then positioned with its long axis mediolaterally and its concavity facing the new trapeziotrapezoid surface. The optimal size was chosen so that the scaphoid surface was entirely covered. Fluoroscopy was performed regularly to check the surface preparation, especially on the most medial part of the joint and to check the implant's stability during full passive flexion–extension and lateral deviation of the wrist. The final implant was positioned. The scaphoid kinematics should be possible in every wrist position. The capsule was closed with resorbable suture and the incision with an intradermal overlock.

The wrist and thumb columns were immobilized for 2 weeks in a heat-molded removable volar splint. The fingers and thumb were free to allow immediate mobilization. Then, self-mobilization of the wrist was resumed, and the volar splint was used at night and during activities until the 6th week.

Clinical and Functional Evaluation

Pain was evaluated with a visual analogue scale (out of 10) at rest and during activity before surgery and at the last follow-up. Grip and pinch strengths were evaluated on the operated and contralateral side using a Jamar hydraulic hand dynamometer and a Jamar hydraulic hand gauge, respectively (Performance Health R, Charleville Mézière, France). The active range of motion (ROM) of the wrist in flexion, extension, ulnar, and radial deviation was measured in degrees (accuracy 3–5°) with a goniometer (Prestige R Medical, Northridge, Los Angeles, United States) on the operated and contralateral sides. The Kapandji thumb opposition score ²³ (out of 10) was also measured before and after surgery. We looked for signs of FCR tendinitis. Functional outcomes were evaluated using the short version of the Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH) (/100) and the Patient-Rated Wrist Evaluation questionnaire (PRWE) (/100) before surgery and at the last follow-up. The time away from work was also recorded. Lastly, patients were asked to rank their overall satisfaction as “poor,” “average,” “good,” or “excellent.”

Radiological Evaluation

Standard A/P and lateral radiographs of the operated and contralateral wrists were made before surgery and at the last follow-up. The stage of STT OA was determined using the Crosby classification. ¹ At the last follow-up visit, we analyzed any anomalies in implant position and looked for arthritic progression in the radiocarpal, midcarpal and TM joint spaces. OA was determined by joint space narrowing and subchondral sclerosis. We calculated the radioscaphoid angle (RSA), capitolunate angle (CLA), and scapholunate angle (SLA) in degrees (accuracy 3°). RSAs greater than 60°, CLAs greater than 15°, and SLAs greater than 70° were considered pathological. ²⁴ A DISI deformity was defined as a CLA more than 15°. ²⁵ The Youm index ²⁶ was also calculated by dividing the carpal height in millimeters by the length of the third metacarpal in millimeters; normal values ranged from 0.51 to 0.57.

Statistical Analysis

Quantitative variables were described by their mean, range, or standard deviation. Qualitative variables were described by their counts and percentages. Student's t test was applied for comparisons of continuous data. The significance level was set at p  < 0.05.

Results

All patients were reviewed for the follow-up examination. The mean follow-up time after surgery was 5 years (range 3–8 years). Thirteen patients (76%) were followed for more than 5 years. Five patients (29%) were actively working at the time of the surgery, with four of them performing heavy manual labor.

Clinical and Functional Outcomes

The clinical results are summarized in Table 1 . Preoperatively, five patients had clinical signs of FCR tendinitis which resolved after surgery. Between the preoperative assessment and the last follow-up, pain levels significantly decreased at rest (5 vs. 0.5, p  < 0.01) and during activity (7 vs. 3, p  < 0.01). There was no significant difference in the mean Kapandji opposition score (9.8 vs. 9.7, p  = 0.6). At the final review, grip and pinch strengths were 88 and 91% relative to the contralateral side. The active ROM in flexion–extension and radioulnar deviation was not significantly modified compared with the contralateral side (119° vs. 121° and 58° vs. 52°, p  > 0.1). The QuickDASH and PRWE functional scores were significantly improved, decreasing from 63 to 23 and 69 to 22, respectively ( p  < 0.01). The employed patients were able to return to work after an average of 7 weeks (range, 4–12 weeks). Eighty-three percent of patients judged their outcome as “excellent” or “good.”

Table 1. Comparison of the clinical and radiographic results (mean and SD) for the study population ( n  = 17 wrists) .

	Preoperative	Last follow-up	95% CI	p -Value
Pain at rest (VAS) (/10)	5 (1.4)	0.5 (1.7)	3.3; 5.5	<0.01
Pain during activity (VAS) (/10)	7 (1.2)	3 (2.4)	3.1; 5.8	<0.01
Kapandji score (/10)	9.8 (0.5)	9.7 (0.7)	−0.3; 0.5	0.6
QuickDASH (/100)	63 (14.2)	23 (22.3)	27; 54	<0.01
PRWE (/100)	69 (13.7)	22 (20.4)	34; 59	<0.01
RSA (°) a	45 (14.7)	43 (14.8)	−11; 14	0.8
CLA (°) a	12.3 (7.5)	14.7 (10.2)	−9.7; 4.5	0.45
Youm index a	0.5 (0.02)	0.5 (0.03)	−0.03; 0.01	0.3
	Last follow-up	Contralateral side	95% CI	p -Value
Flexion–extension (°)	121 (13.1)	119 (15.6)	−13.3; 7.7	0.6
Radioulnar deviation (°)	52 (11.6)	58 (14.2)	−3.8; 15.1	0.2
Grip strength (Kg.F)	20 (8.8)	23 (12.5)	−5.3; 10.8	0.5
Pinch strength (Kg.F)	7 (7.2)	7.8 (6.7)	−4.6; 5.3	0.9

Abbreviations: CI, confidence interval; CLA, capitolunate angle; PRWE, Patient-Rated Wrist Evaluation; QuickDASH, Quick Disabilities of the Arm, Shoulder, and Hand; RSA, radioscaphoid angle; SD, standard deviation; VAS, visual analogue scale.

^a38% of the preoperative radiographs were not available.

Radiological Outcomes

Not all preoperative radiographs were available ( Table 1 ). STT OA was stage 2 in nine cases and stage 3 in nine cases before the procedure ( Fig. 1 ). No patient had clinical or radiographical TM OA preoperatively. At the review, four (23%) patients had asymptomatic TM OA. Five (29%) patients had chondrocalcinosis diagnosed on radiographs. Between the pre- and postoperative periods, there were no significant changes in the RSA ( p  = 0.7), CLA ( p  = 0.4), and SLA ( p  = 0.9). All patients had normal angle values except for four, who had a CLA between 15° and 35°. In three cases, the preoperative DISI failed to be corrected. In the last case, DISI appeared after the procedure. One out of four patients had an SLA >70° relative to a preoperative scapholunate instability. Also, there was no significant difference in the Youm index ( p  = 0.3).

Fig. 1.

( A ) Radiographs of a left wrist with isolated STT OA, stage 2 in the Crosby classification ( arro w). ( B ) A/P and C. Lateral radiographs at 5 years' follow-up with the Pyrocardan implant ( arrows ). OA, osteoarthritis; STT, scaphotrapeziotrapezoid.

There was one case of asymptomatic dislocation of the implant ( Fig. 2 ). Calcification around the trapezium or the distal scaphoid was found in four cases ( Fig. 3A ). In one patient, we found a slight progression of the styloscaphoid OA from the preoperative condition.

Fig. 2.

( A ) A/P radiograph and ( B ) lateral radiograph of a right wrist showing Pyrocardan implant dislocation ( arrows ), 3 months after the procedure. On the lateral view, there is a DISI malalignment of the lunate. DISI, dorsal intercalated scapholunate instability.

Fig. 3.

( A ) A/P radiograph of a left wrist at 5 years' follow-up showing trapezium and trapezoid calcifications ( arrow ). No calcification was present in the immediate postoperative period. ( B ) Same wrist after revision surgery at 5 years' follow-up. The calcification has been removed as shown by the arrow .

Complications and Surgical Revisions

There were no cases of infection or wound dehiscence. One patient developed complex regional pain syndrome that resolved with physiotherapy and analgesic drugs. The survival rate of the implant without reoperation was 94.5%. No implants had to be removed but one patient (5.5%) required surgical revision 62 months after the initial procedure because of symptomatic calcification around the trapezium and trapezoid. After removing the bone spurs ( Fig. 3B ) without changing the implant, the patient became asymptomatic.

One dislocation happened a few weeks after the surgery. No further surgery was necessary because the patient did not complain of pain, loss of strength, or functional deficit even at the end of the follow-up.

Discussion

Based on our study's findings, at a mean follow-up of 5 years, STT arthroplasty using a Pyrocardan implant to treat isolated STT OA leads to a significant reduction in pain, with improved strength and functional scores.

Our clinical outcomes are consistent with those of similar published case series using pyrocarbon implants in the STT joint ( Table 2 ). All of them showed that a pyrocarbon implant is well tolerated in the STT joint. Moreover, they all found a significant decrease in pain. In our study, active ROM in flexion–extension and lateral deviation was 102 and 90% of the contralateral side, respectively. Grip and pinch strengths were not significantly decreased compared with the opposite side ( p  < 0.05). At 2 years' follow-up with the Pyrocardan implant, Gauthier et al ¹⁰ reported improved grip and pinch strength (109 and 140%) relative to the preoperative condition. They also found no significant changes in ROM except in wrist extension ( p  < 0.01). Finally, the QuickDASH and PRWE scores were significantly improved. As for the STPI pyrocarbon implant, grip strength was between 82 and 133% (average 114%) of the preoperative value or nonoperated side in all published studies. ^{8 13 14 15 16 17 18} Low ¹⁴ was the only author who reported the percentage of wrist motion compared with the nonoperated side with 107% in flexion–extension and 72% in lateral deviation. Three out of six studies which determined the DASH score reported an average score of 29.

Table 2. Clinical results from the main published studies on STT Pyrocarbon implants.

Literature	Pyrocarbon implant	Cases	Mean FU (mo)	ROM FE – RUD (% of contralateral side or preoperative)	Grip – pinch strength (% of contralateral side or preoperative)	Functional scores	Revision surgery (%)
Pequignot et al (2005)	STPI	15	48	n/a – n/a	n/a – n/a	n/a	None
Pegoli et al (2006)	STPI	10	19	n/a – n/a	133–140	D: 39	2 dislocations (20)
Mathoulin and Darin (2006)	Arthroscopic + STPI	13	20	n/a – n/a	n/a – n/a	n/a	2 dislocations (15)
Low and Edmunds (2007)	STPI	9	16	107–72	82–85	D: 21	None
Lluch et al (2013)	STPI	21	29	n/a	84–92	n/a	None
Marcuzzi et al (2014)	STPI	8	77	87 in total	n/a – n/a	n/a	None
Pegoli et al (2016)	Arthroscopic + STPI	13	24	n/a – n/a	135–168	D: 39	None
Gauthier et al (2017)	Pyrocardan	22	24	89–93	109–140	QD: 19; PRWE: 14	1 RSI/ 1 calcification (9)
Average		15	26	98–82 a	114–125	QD: 29; PRWE: 14	0.75
Median		13	24	98–82 a	109–140	/	0
Our study	Pyrocardan	18	63	109–90	88–91	QD: 23; PRWE: 22	1 calcification (6)

Abbreviations: D, Dash score; FU, follow-up; n/a, not available; QD, QuickDASH score; ROM FE – RUD, range of motion in flexion–extension – radioulnar deviation; RSI, radioscaphoid impingement; STT, scaphotrapeziotrapezoid; VAS, visual analogue scale.

^aExclusion of the Marcuzzi results.

No significant changes were found in the radiological outcomes between the pre- and postoperative periods for the RSA, CLA, SLA, or the Youm index ( p  > 0.05). As a whole, the wrist architecture and biomechanics do not seem to be modified by the implant, 5 years later. In contrast to the Gauthier et al's study, ¹⁰ which had not found any DISI of the lunate at 2 years, we discovered four of them. In three cases, the DISI deformation was present before the arthroplasty: in the first case, scapholunate instability was present preoperatively, which can explain the pre- and postoperative DISI. In the two other cases, patients had a bilateral DISI before the surgery without any complaints. Arthroplasty with the Pyrocardan implant did not change the three-dimensional configuration of the carpal bones. For the last case, DISI malalignment appeared after the surgery and can be explained by early dislocation of the implant. We can ask ourselves the following two questions: could the Pyrocardan implant be indicated when a preoperative DISI is present or when the scaphoid is over horizontalized? Would an intracarpal arthrodesis such STT arthrodesis be more appropriate? A comparative study would be required to answer these questions.

The only case of dislocation in our study appeared a few weeks after the procedure. No revision surgery was performed because the patient did not complain of pain and had regained full function of his hand and wrist. This is the first reported dislocation when the Pyrocardan implant was used in the STT. No such complication was found in the Gauthier et al's study. ¹⁰ This instability may result from insufficient bone resection, especially on the trapezoidal side, which is the most difficult to access, from excessive resection of the trapezoid-trapezoidal surfaces resulting in an insufficiently constrained implant and finally, from pre-existing or iatrogenic excess STT ligamentous lesions. In our particular case, insufficient bone resection seems to be the cause of the dislocation, medially constraining the implant, with a tendency to expel it laterally. In the TM location, Gerace et al ¹⁹ and Logan et al ²⁰ did not find any dislocation using the Pyrocardan implant. With the STPI implant, several cases of dislocation have been described whether in open surgery or under arthroscopy. Mathoulin and Darin ⁸ and Pegoli et al ¹⁷ found two cases of dislocation each. The explanation given by the authors was that their patients were operated early in the learning curve and that the dislocation occurred because of inadequate resection of the distal scaphoid and/or damage to the STT ligaments. The STPI implant's architecture may also have been an intrinsic factor contributing to instability. Indeed, its circular convex shape does not seem to fit properly with the convex anatomy of the distal scaphoid and with the more rectangular shape of the STT joint. Finally, because of its thickness, too much bone resection is probably needed with a higher risk of damaging the STT ligaments.

Although we identified four cases of periarticular bone calcification, only one required revision. This male patient had to be reoperated 5 years after the arthroplasty because of symptomatic calcifications around the trapezium and scaphoid, without any modification on the implant. In the Gauthier et al's study, ¹⁰ one patient had to be reoperated because of this type of complication. To avoid such a complication, we advise carefully removing all bone debris remaining around the trapezium and trapezoid.

Like the STPI implant, ^{8 17} the Pyrocardan could be introduced in the STT joint using arthroscopic procedure but no studies have been published so far on this topic. However, we think there is no additional benefit of using arthroscopy because a capsulotomy needs to be performed to insert the implant in all cases.

The Pyrocardan implant can be introduced either by a radial or a volar approach. We usually use an anterior approach for two reasons: the first is to obtain good exposure of the STT joint space, allowing complete bone resection while safeguarding the stabilizing ligaments. The second is the possibility of carrying out a synovectomy of the FCR tendon, often inflamed in STT OA, which is not possible through a radial approach.

Other surgical techniques exist to treat STT OA. STT arthrodesis has long been used and provides good results in the medium and long term on pain, functional scores, and strength. ^{12 27 28 29 30 31} However, this procedure is not free from complications; nonunion has been reported in 0 to 31% of cases ^{12 27 30 31 32 33} while radiocarpal and/or midcarpal OA degeneration also occurs. ^{33 34 35 36} It seems to be a good choice if DISI malalignment is present and for heavy manual workers. ¹² Nevertheless, strict compliance with the different surgical steps is essential to minimize the risk of nonunion. The scaphoid's positioning is also important to maximize wrist mobility. ³⁷ Other authors prefer resection of the distal pole of the scaphoid, ⁹ arthroscopic procedures, ^{8 38} or trapeziectomy. ^{11 39} Most of the time, the clinical results are satisfactory. However, some cases of DISI malalignment have been reported when performing distal scaphoid resection, with or without arthroscopy, or trapeziectomy. ^{9 40 41} This can be due to the STT ligament complex being damaged because of overresection. More recently, Humada Álvarez et al ⁴² reported the results of resurfacing arthroplasty of the distal pole of scaphoid with encouraging short-term results. At 26 months of follow-up, strength and wrist mobility was restored to more than 90% on the contralateral side. In a study comparing four surgical procedures (total trapeziectomy, distal partial scaphoidectomy alone, and partial scaphoidectomy with tendon or pyrocarbon interposition), Lafaye et al ⁴³ found no identifiable differences in postoperative ROM and no surgical technique was superior at halting the progression of intracarpal misalignment.

Our study has its limitations. First, it was a retrospective study, and we did not compare different types of surgical procedure. Second, not all preoperative radiographs were available. Third, we had a limited sample size although it was within the range of similar published studies. However, we have the longest follow-up in the literature. Finally, we did not compare the two available pyrocarbon implants (STPI and Pyrocardan).

In the medium term, using a Pyrocardan implant to treat STT OA is effective at reducing pain, increasing grip strength, and maintaining wrist mobility. It provides a high rate of patient satisfaction. Nevertheless, it is necessary to remain cautious during the surgical procedure with respect to the STT-stabilizing ligaments and by being careful about the bone preparation of the trapeziotrapezoid surface. In addition, careful removal of all bone fragments seems important to minimize the risk of postoperative periarticular calcification. Another study is needed to extend the follow-up period to ensure these results are maintained on a long-term basis.

Funding Statement

Funding None.