Outcome study

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Methods

A total of 21 MP joint arthroplasties in 19 patients were performed for OA over the past 3 years at the authors' institution. Ten of these patients were part of a prospective Food and Drug Administration (FDA)-approved study and the remaining 9 opted out of the study protocol, but were reviewed retrospectively. All patients presenting with OA of the MP joint were requested to participate in the study.

All patients completed questionnaires preop-eratively, and at 6 weeks, 12 weeks, 6 months, and 1 year following surgery. The questionnaires inquired about patient age, sex, race, hand dominance, history of trauma, and previous surgical procedures performed on the involved joint. Patients were asked to give their major reason

Fig. 11. Extensor mechanism is closed with radial imbrication.
Fig. 12. (A) Dynamic extension splint is worn after the first postoperative visit for the first 3 to 4 weeks as multiple joints are replaced. (B) Modification of the splint to allow for proximal interphalangeal (PIP) flexion; static splints are worn at night.

for proceeding with surgery. They were also asked to document their employment status preopera-tively and at all postoperative time points.

Patients recorded their postoperative progress using visual analog scales. Visual analog scales evaluated pain, function, and cosmesis of the finger. All findings were marked on a linear, nongraduated scale from 0 to 100. These markings were measured with a ruler to determine the percent rating of pain, the percent of normal functioning of the digit, and percent of normal appearance as subjectively determined by the patient.

Measurements of MP joint flexion, extension lag, and radial or ulnar deviation were obtained. Oppositional pinch and grip strengths were obtained for all time points apart from the 6-week postoperative period, where it was felt that over-exertion may displace the implant or cause soft-tissue injury. All data were collected using the standardized computer assisted hand measurement tools (Dexter system). Strength measurements were performed in triplicate and averaged. All data were organized on a standard excel spreadsheet and tabulated. A student t-test was used for all statistical comparisons.

Radiological assessment was performed pre-operatively, and 1 week, 6 weeks, 12 weeks, 6 months, and 1 year postoperatively. Preoperative standard anteroposterior (AP), lateral and oblique radiographs of the involved digit were assessed for joint narrowing, osteoporosis, subchondral erosions, joint ankylosis, and cyst formation. Joint reduction, subluxation, or dislocation were also documented. Evidence for axial subsidence, stem migration, resorption stress shielding, increasing radiolucent seam, periprosthetic erosions, and heterotopic bone formation was also evaluated.

Results

Of the 21 MP joints (19 patients) treated for OA with pyrolytic carbon (Ascension, Austin, Texas) arthroplasty, 20 were primary joint replacements and 1 was a revision following a fracture of a silicone implant. The average patient age was 57.2 years (range 31-75). Five patients (26.3%) were female and 14 (73.7%) were male. Twenty-six point three percent of patients admitted to smoking. The average duration of symptoms averaged 2.6 years (range 1-7 years). A history of direct trauma to the affected joint was recalled in 5 patients (26.3%). Five patients had undergone previous surgery on the affected joint before arthroplasty. At presentation, 100% of patients complained of pain with an average intensity of 75.2 on the visual analog scale (range 0-100). On average, patients felt their involved joint functioned only 23.1% of normal (Table 1). Goals of surgery, as reported by the patients, were pain control in 74%, improvement in function in 21%, and improvement in both pain and function in 5%.

Preoperative radiographic assessment showed that 43% of affected joints showed some evidence for subluxation; there were no cases of frank dislocation. Joint narrowing was noted in 85.7% of patients, subchondral erosion was noted in 57%, and heterotopic ossification was seen in 38% of patients. There were no cases of joint ankylosis.

A total of 10 index MP and 11 long-finger MP joints were treated. Concomitant procedures

Table 1

Range of motion and strength

Table 1

Range of motion and strength

ROM

MP flexion

MP ext (Lag)

Opp pinch (kg)

Grip (kg)

Bout

SN

Pre-op

65.5

21.1

1.4

20.3

0

0

6 weeks

63.2

11.2

NA

NA

0

0

12 weeks

66.1

14.2

3.3

23.4

0

0

6 months

69.1

12.7

2.2

30.4

0

0

1 year

73.2

15.2

3.2

28.1

0

0

% increase from pre-op

12.8

-28.0

125.9

38.2

Abbreviations: Bout, boutonniere; ext, extension; Lag, extension deficit; NA, not available; Opp, oppositional; ROM, range of motion; SN, swan neck

Abbreviations: Bout, boutonniere; ext, extension; Lag, extension deficit; NA, not available; Opp, oppositional; ROM, range of motion; SN, swan neck included one intrinsic tendon release, four synovectomies, and two extensor tendon realignments. No intraoperative complications were noted.

The average duration of follow-up was 14 months (range 3-38.5). Range of motion (ROM) at the 1-year time point was expressed as a change from preoperative values. The preoperative average ROM was from minus 21° of extension to 65° of flexion at the MP joint. Postoperative, the average motion arc was seen to increase from minus 15° of extension to 73° of flexion. This represented a MP joint flexion increase of 12.8% (P— 0.17) and MP extension lag decrease of 28.0% (P — 0.18). Despite the improvement in motion, neither change reached significance. Final oppositional pinch increased 125.9% (P — 0.02) over preoperative values and grip strength improved nearly 40% (P — 0.04) (see Table 1). There were no cases of boutonniere or swan neck deformities developing during the postoperative follow-up.

All patients reported pain at initial presentation; this significantly declined throughout the postoperative course. Only 2 of the 19 patients noted any pain at 1 year. The analog pain scale averaged 73 preoperatively (scale 0 — no pain, 100 — worst pain possible) and 8.5 at final follow-up, an 88.4% decrease (P— 0.0004). The patients' grading for the functionality of the involved digit increased from 20.1% of normal anticipated function to a final value of 86.6%, an increase of 330.4% (P — 0.0002). Appearance of the digit was also felt to improve. Digital cosmesis approval rating rose from 62.7% to 93.6% at 1 year after surgery, an increase of 49.3 (P — 0.01) (Table 2).

Preoperatively, nine patients were working full-time, two part-time, two were on disability, four were retired, one unemployed, and one patient was a homemaker. At final follow-up, eight patients had returned to their preoperative work status (seven full-time, one part-time); one patient was able to regain full-time employment following arthroplasty. One patient in the study had remained retired and one became a student. Another patient retired from full-time work, but not because of disability or pain attributable to the surgery. A single patient remained on disability until lost to follow-up at the 1-year time point. Two patients are pending the 1-year follow-up, although one was retired at the time of surgery and the second had already returned to part-time employment by the 6-month mark. Data were not available on the four final patients: one home-maker, two retired preoperatively, and one employed full-time. In summary, 75% of patients returned to their previous employment status. In addition, one patient came out of retirement to regain full-time work status because of his improved function. Furthermore, one patient who

Table 2

Patient outcome measures

Table 2

Patient outcome measures

Pain

Analogue pain

Function

Appearance

Satisfaction

Group

(% occurrence)

(% occurrence)

(% of normal)

(% of normal)

(% patients)

Pre-op

100

73.1

20.1

62.7

6 weeks

31.6

8.9

68.3

81.2

100

12 weeks

15.8

7.1

78.3

86.1

100

6 months

10.5

11.8

75.3

82

94.7

1 year

10.5

8.5

86.6

93.6

94.7

did not return to full-time employment had retired, but not as a result of disability.

There were five (26.3%) complications; two were considered minor. One patient required extensor tendon suture removal at 6 weeks for irritation. A second patient developed MP joint swelling at 6 weeks because of joint capsule irritation, which resolved with extension splinting. There were three major complications: one case of extensor tendon rupture, one case of implant dislocation 4 months following surgery, and one case of chronic pain requiring implant removal. This last complication occurred in the index finger MP joint of a carpenter, who despite arthroplasty continued to complain of chronic pain inhibiting heavy labor. Re-exploration found no problem of wear present within the implant. Despite reexploration. the patient eventually requested a ray amputation 1 year following initial surgery to allow him to continue his job as a carpenter. The patient continues to work full-time. Interestingly, of the three patients experiencing a major complication, all had had prior surgery on the involved joint and one patient had had surgery for revision of a fractured silicone implant. There did not appear to be any correlation between complications and smoking status, medications, or past medical history.

Seven of the 19 total patients have been followed beyond 1 year, with an average postoperative assessment at 25 months (range 14-39). Within this group none reported pain. All patients had returned to their normal activities, including heavy labor employment and sport-related activities such as golfing. All patients who had this long-term follow-up were very satisfied with their outcome.

Radiographic assessment

Radiographically, there was a single case of dislocation at 4 months following surgery. Peri-prosthetic erosion was noted in one patient at the 12-week follow-up and in 1 patient at the 1-year time point. The same patient who had the periprosthetic erosion at 1 year also represented the only case of resorption stress shielding seen at the 1-year mark. Despite radiographic findings, this patient has an excellent functional outcome and no pain.

An increase in the size of the radiolucent seam surrounding the implant is seen in all patients at 1-year follow-up, and in 62.5% of patients at 6-month follow-up. This appears to represent an incorporation of the implant stem into the surrounding bone, demonstrating a normal or anticipated radiolucent interface. Despite increase in seam size, none of the implants have demonstrated evidence of loosening or migration. There were no cases of axial subsidence, stem angular migration, heterotopic bone, or new cyst formation within this series (Table 3) (Fig. 13).

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