This section describes efficacy outcomes from the published literature that the committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the interventional procedure overview.
4.1 In a randomised controlled trial (RCT) of 23 patients needing digital nerve repair comparing processed nerve allograft (PNA) with treated bovine graft at 12‑month follow-up, static 2‑point discrimination assessment (s2PD, which tests the ability to discern the difference between 1 and 2 static pressure points) was statistically significantly better in the PNA group (n=5) than the bovine graft group (n=7; 5±1 mm versus 8±5 mm, p<0.05). In the same study, moving 2‑point discrimination assessment (m2PD) was not statistically significantly different between the PNA group and the bovine graft group (5±1 mm versus 7±5 mm, p>0.05) at 12‑month follow-up. In a non-randomised comparative study of 153 patients needing digital nerve repair comparing PNA repair (n=72) with tension-free suture nerve repair (n=81), s2PD scores (excellent plus good, defined as the ability to distinguish between 2 static pressure points at a maximum distance of 15 mm) were not statistically significantly different between the PNA group (67% [48/72]) and the tension-free suture group (64% [52/81]) at 6‑month follow-up (p=0.749). In a case series of 17 patients with digital nerve injuries treated by PNA grafting, s2PD was excellent or good in 78% (14/18) of digits repaired, at a mean follow-up of 15 months. In the RCT of 23 patients, Semmes–Weinstein monofilament test (testing of pressure threshold using a monofilament; range: 2.833=normal sensation to 6.650=residual sensation) was statistically significantly better in the PNA group than the treated bovine graft group (3.6±0.7 versus 4.4±1.4, p<0.05) at 12‑month follow-up. In the same study, thermal sensation was totally improved from baseline at 12‑month follow-up and not statistically significantly different between the treatment (PNA group: from 7% [1/14] to 100% [6/6] and bovine graft group: from 33% [3/9] to 100% [7/7]).
4.2 In a case series of 64 patients needing nerve repair in the upper extremity and treated by grafting using PNA, there was meaningful recovery in 75% (48/64) of all patients. Univariate analysis showed that distal sites of injuries have a statistically significantly higher likelihood of recovery than proximal upper limb sites (odds ratio [OR] 5.606, 95% confidence interval [CI] 1.663 to 18.903; p<0.05). In the same study, discontinuities smaller than 30 mm had a statistically significantly greater likelihood of meaningful repair than those greater than 50 mm (OR 14.333, 95% CI 2.143 to 95.848; p<0.05). In a case series of 26 patients with lingual nerve and inferior alveolar nerve discontinuities treated by PNA grafting, meaningful sensory recovery was assessed using a neurosensory test improvement tool (ranging from normal=best, through mild, moderate and severe to complete=worse). At 12‑month follow-up, neurosensory test improvement scores were normal in 52% (12/23), mild in 9% (2/23), moderate in 26% (6/23) and severe in 13% (3/23) of patients. In the same study, neurosensory improvement was reported in 86% (12/14) of patients with discontinuities 8–20 mm in length and 89% (8/9) of patients with discontinuities 30–70 mm in length.
4.3 In the RCT of 23 patients, disability of the arm, shoulder and hand score (DASH: 0=no disability, 100=most severe disability) was not statistically significantly different between the PNA group (5±6.5) and the bovine graft group (8±6.3) at 12‑month follow-up (p=0.318).
4.4 In a case series of 108 patients needing nerve repair, there was no sensory recovery because of graft failure in 5% (4/76) of patients at last follow-up and surgical revision was needed.
4.5 In the RCT of 23 patients, at 12‑month follow-up, pain measured using a visual analogue scale (VAS, 0=no pain, 10=extreme pain) had improved from baseline in both groups (PNA group: from 4.7±3.4 to 0.5±0.6; treated bovine graft: from 4.4±2.1 to 0.9±1.0) but there was no statistically significant difference between the groups (p=0.432). In another case series of 26 patients needing PNA after resection of neuromas of the foot and ankle, mean ordinal pain score (0=no pain to 10=worse pain) statistically significantly reduced from 7.5 points at baseline to 4.9 points at a mean 66‑week follow-up (difference 2.6, range +2.0 to −8.0; p=0.016). In the same study, patient reported outcome measurement information system scores were used to assess the impact of pain on patients' behaviour and daily function (reported as T‑scores with a population mean of 50 and a standard deviation of 10). Pain behaviour T‑score decreased by 7.3 (range+2.0 to −22.0) from 63.0 at baseline (percentile decrease of 24%, p<0.003). Pain interference T‑score decreased by 11.3 (range +2.0 to −27.0) from 68.0 at baseline (mean percentile change of 31%, p<0.003). In a case series of 17 patients with digital nerve injury treated by grafting with PNA, pain (measured using a VAS: 0=no pain, 10=extreme pain) worsened in 1 patient (VAS score increased from 5 at baseline to 8 at 15‑month follow).
4.6 In the non-randomised comparative study of 153 patients, difference in satisfaction rate was not statistically significantly different between the PNA group and the tension-free suture group (2.02%, 95% CI −6.07 to 10.87) at 6‑month follow-up.
4.7 The specialist advisers listed key efficacy outcomes as re-innervation of target organs, nerve regeneration rate, clinical sensory and motor outcome scales, and patient reported outcomes.