The Referrer Matters. Musculoskeletal Surgical Conversion Rates: A Systematic Review With Meta-Analysis

Background

Musculoskeletal conditions are a leading cause of disability and persistent pain globally. ¹ As much of the world’s population becomes older, and increasingly sedentary, the prevalence of musculoskeletal disease is expected to increase, thereby amplifying demand for care^2,3 and posing challenges for health and social care delivery. Surgical services will shoulder much of this burden, with rates of common procedures such as knee arthroplasty, predicted to increase 276% by 2030. ⁴ While costly to governments and healthcare funders, timely surgical activity is important for society as it returns injured and disabled individuals to work and activity, thereby supporting productivity and societal economic stability. Furthermore, surgical departments such as orthopaedics are critical to the financial viability of hospitals, with 35% of elective surgery revenue and 23% of net hospital income resulting from elective surgery for musculoskeletal conditions. ⁵ Thus, efficient musculoskeletal care is crucial for both health services and society.

A common measure used to assist organisational understanding of efficiency in surgical pathways is the surgical conversion rate (SCR), which represents the proportion of referrals that convert to surgery. This is calculated by dividing the number of surgical cases by the total number of cases seen and expressed as a decimal value or multiplied by 100 for a percentage value. ⁶ A high SCR is associated with effective referral pathways, efficient utility of the surgical workforce ⁷ and greater service revenue. ⁸ In contrast, with a low SCR proportionally fewer referred patients require surgery. This may be associated with longer waiting times for patients and reduced organisational productivity, for example if a significant amount of surgeons’ time is consumed by non-surgical cases.

Given the importance to health organisations of understanding efficiency and demand for services, ⁹ surprisingly little is known about SCRs for musculoskeletal referrals. Prior reviews have focused on orthopaedic waiting list management by professional groups such as physiotherapists in orthopaedic screening services (where patients who were referred to surgeons are instead seen by experienced physiotherapists), and reported that appropriately trained physiotherapists in these services can effectively triage, manage musculoskeletal referrals and improve SCR^10-13 but the actual impact on SCRs has been less clear. ¹¹ The SCR has been estimated with a wide range of 25% to 91% by a prior review specifically of extended scope physiotherapy services ¹⁴ and no meta-analysis has been conducted. While these findings highlight potential efficiency gains from interprofessional collaboration, several knowledge gaps continue to hinder service design; typical SCRs in orthopaedic/musculoskeletal settings are poorly understood, the impact of varying referral rules and pathways (based on professional groups) have not been clearly compared and methodological variables impacting SCR reporting have not been highlighted. Greater intelligence about SCRs could assist evaluation of referral processes, support benchmarking across services and aid efficient service redesign. Therefore, the primary aim of this review was to report surgical conversion rates for musculoskeletal disorders and quantify the impact on SCR of referrals from different professional groups. The secondary aim was to describe methodological factors that impact SCR reporting.

Methods

A systematic review with meta-analysis was undertaken, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). ¹⁵ The protocol was registered on Open Science Framework (OSF), Registration: osf.io/c7dkz/ DOI: 10.17605/OSF.IO/C7DKZ.

Critical appraisal

Two authors (DM and WH) independently appraised included studies using the Joanna Briggs Institute (JBI) Appraisal Tools for cross-sectional studies ²³ as consensus deemed this the most appropriate tool for appraising studies with respect to the SCR focus of this review. Discrepancies were resolved through discussion, or involvement of a third author if required. The checklist comprised 8 questions, which were assigned a value of 1 when scored as ‘yes’ and a value of 0, when scored as ‘no’ or ‘unclear’. Total scores out of 8 are recorded in Table 1 and a detailed breakdown of scoring for each included study appears as supplementary information.

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Table 1.

Summary of included studies.

Study	Country setting	Study design	Age (mean or other indicator)	Condition/s	Referrer	No. seen by orthopaedics/neurosurgery	No. deemed surgical	How deemed surgical	Appraisal ( /8)
Aiken and McColl 24	Canada Public	Inter-rater reliability	(Arthroplasty service)	Hip/Knee	GPs	38	25	Surgical opinion	5/8
Ashmore et al 25	Ireland Public	Retrospective audit	46	Knee	Physiotherapy/Screening Service	50	42	Had surgery	7/8
Bath et al 26	Canada Private	Retrospective audit	51	Spine/hip/knee	Physiotherapy/Screening Service	98	30	Surgical opinion	5/8
Bernstein 27	UK Public	Retrospective audit	(Not stated)	Mixed	Physiotherapy/Screening Service	455	318	Surgical opinion	3/8
Blackburn et al 28	Australia Public	Retrospective audit/cohort	(Not stated)	Spine LBP	Physiotherapy/Screening Service	17 a	9	Had surgery	6/8
Burn and Beeson 29	UK Public	Prospective cost/service evaluation	(Not stated)	Mixed	Physiotherapy/Screening Service	38	27	Listed for surgery	5/8
Campagna-Wilson et al 6	Canada Military	Survey/retrospective service evaluation	42	Mixed	Physiotherapy/Screening Service	102	44	Surgical opinion	7/8
					All doctors	119	36
Candy et al 30	UK Public	Retrospective cross-sectional	(Not stated)	Mixed	Physiotherapy/Screening Service	462	237	Had surgery	6/8
Goodman et al 31	USA Military	Prospective service evaluation	(18+)	Mixed	All doctors	731	140	Had surgery	7/8
Gwynne-Jones et al 32	New Zealand Public	Prospective cohort	67	Hip/Knee	Physiotherapy/Screening Service	143	118	Listed for surgery	7/8
Hattam 33	UK Public	Retrospective cross-sectional	(Median 36-55)	Mixed	Physiotherapy/Screening Service	170	89	Had Surgery	7/8
Heywood 34	UK Military	Prospective service evaluation	(Military personnel)	Spinal	Physiotherapy/Screening Service	25	15	Had surgery	4/8
Hourigan and Weatherley 35	Ireland Public	Prospective service evaluation	47	Spine	Physiotherapy/Screening Service	14	6	Had surgery	5/8
Kara et al 36	Turkey Public	Retrospective cohort	22	Mixed	Sports Physicians	155	110	Surgical opinion	7/8
							76	Had surgery
Lyons et al 37	Ireland Public	Prospective service evaluation	(Not stated)	Shoulder	Physiotherapy/Screening Service	201	56	Listed for surgery	6/8
							50	Had surgery
Marks et al 38	Australia Public	Prospective cost of illness	57	Shoulder	GPs	277	61	Had surgery	7/8
Mathieu et al 39	Canada Public	Retrospective cross-sectional	61	Spine LBP	All doctors	500 a	112	Surgical opinion	8/8
Mayman and Yen 40	Canada Public	Prospective service evaluation	(Not stated)	Spine (thoracic or LBP)	All doctors	142 a	27	Surgical opinion	6/8
Menzies and Young 41	USA Public	Retrospective cohort	51	Mixed	Sports Physicians	118	80	Surgical opinion	7/8
Murphy et al 42	Ireland Public	Retrospective service evaluation	45	Spine LBP	Physiotherapy/Screening Service	16	4	Had Surgery	6/8
Napier et al 43	Canada Public	Prospective service evaluation	47	Shoulder/Knee	Physiotherapy/Screening Service	11	9	Listed for surgery	7/8
O'Farrell et al 44	Ireland Public	Retrospective service evaluation	50	Shoulder/Knee	Physiotherapy/Screening Service	110	80	Listed for surgery	7/8
Oldmeadow et al 45	Australia Public	Prospective inter-rater observation	58	Spine/Shoulder/Knee	GPs	38	7	Surgical opinion	7/8
Roland et al 46	UK Public	Prospective survey	(Not stated)	Mixed	GPs	499	81	Listed for surgery	6/8
Speed and Crisp 47	UK Public	Retrospective audit	(Not stated)	Mixed	All doctors	362	111	Listed for surgery	5/8
Stilwell et al 48	NZ Public	Retrospective audit	73	Hip/knee	Physiotherapy/Screening Service	133	87	Listed for surgery	7/8
Walsh et al 49	Australia Public	Retrospective service evaluation	57	Foot/Ankle	All doctors	72	9	Listed for surgery	7/8
					Podiatry/Screening Service	46	35
Wood et al 50	UK Public	Prospective service evaluation	(Not stated)	Spine	Physiotherapy/Screening Service	171	138	Surgical opinion	6/8
							97	Had surgery

a

Neurosurgery referral (remainder are orthopaedic). If only LBP then this is written next to spine. Mixed=more than 3 conditions.

Results

General description of studies

Twenty-eight studies with a combined total of 5358 patients, met the inclusion criteria (Figure 1). Key information from each study is summarised in Table 1. Three studies included referrals to neurosurgery for spinal pathology,^28,39,40 while the remainer involved referrals to orthopaedic services. A wide spectrum of musculoskeletal disorders was represented across the included studies; 10 reported surgical conversion rates in cohorts referred with a mixture of musculoskeletal presentations, while the remainder pertained to a specific region or small groups of conditions as detailed in Table 1.

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Figure 1.

PRISMA diagram. ¹⁵

Study quality was generally moderate to high, with scores ranging from 3 to 8 out of a possible total of 8 (Table 1). Full details are reported in the Supplemental File. As all studies reported observational data pertaining to surgical conversion rates, outcome measures were generally well reported. All studies used appropriate statistics for our outcome of interest (SCR). However confounding factors were seldom reported or managed and while discussion of the impact of variable methodologies used to deem patients as surgical (such as opinion vs having surgery) was greatly absent, 3 studies tackled this by simultaneously reporting 2 methods.^36,37,50

Data pertaining to referrals solely from GPs were extracted from 4 studies, sports physicians in 2 studies, a combined group referred to as all doctors in 6 studies and from a screening service in 18 studies (Table 1). All but 2 of these screening services were solely staffed or led by physiotherapists, one involved a combination of physiotherapist and nurse, ³² one involved a podiatrist. ⁴⁹ Two studies presented data from more than one referrer-group, comparing the orthopaedic SCR between a physiotherapy-led screening service and referrals from all doctors, ⁶ and another comparing the orthopaedic SCR in referrals from a podiatry screening service compared with referrals from all doctors. ⁴⁹ The remaining studies presented data from one referrer-group (Table 1).

Surgical conversion rates

Meta-analysis of pooled SCR data, separated into referrer-groups, is presented in Figure 2. Results demonstrate clear differences in orthopaedic SCR according to the referrer. The lowest SCR at 23% was for referrals to orthopaedics from all types of doctors (0.23, 95% CI 0.18-0.27), SCR for referrals from GPs was similarly low at 28% (0.28, 95% CI 0.12-0.52). Higher SCRs were evident from predominantly physiotherapy – led screening services at 61% (0.61, CI 0.50-0.70) and sports physicians at 70% (0.7, CI 0.64-0.75).

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Figure 2.

Pooled SCR for referrals from (a) all doctors, (b) GPs only, (c) screening services and (d) sports physicians, using the highest reported SCR from each study out of opinion, listed or had methodologies. Events = surgical cases, Total = total referrals.

Methodological factors impacting the reporting of SCR

The methodology used to deem a case surgical varied across included studies. Ten studies reported data in which the surgeon’s opinion was used to deem a case surgical, 9 in which patients were listed/consented for surgery and 12 studies presented data pertaining to cases in which surgery had been performed (Had). While most studies reported only one of these methods, 3 studies used more than one method,^36,37,50 in each case demonstrating that the SCR is highest when the surgeon’s opinion is used, next highest when surgical listing/consent is used and lowest when actual surgeries performed (Had surgery) is used as the measure to determine surgical cases (Table 1). For this most conservative category of surgery performed (Had surgery), only screening services yielded more than one study; the rate was 51% based on 9 studies (0.51, 95% CI 0.38-0.63), with metanalysis appearing in Figure 3.

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Figure 3.

Pooled SCR for referrals from (a) all doctors, (b) GPs only, (c) screening services and (d) sports physicians, using only data from studies reporting SCR in which patients had surgery performed (Had). Events = surgical cases, Total = total referrals.

Discussion

This is the first systematic review to comprehensively synthesise musculoskeletal SCR data collated from across the spectrum of referrer types, the first to highlight methodological attributes of research that impact SCR interpretation and the first to present meta-analysis of pooled SCR data. Results demonstrate that the model of care or professional group managing referrals into the surgical unit, has substantial impact upon the SCR in that unit. This highlights that the efficiency of a surgical service is dependent upon potentially multi-professional primary and secondary care musculoskeletal services that support it. Notwithstanding the modest number of included studies and high heterogeneity, pooled observations reveal that when physiotherapy-led screening services (61%) or sports physicians (70%) are responsible for referring patients, orthopaedic SCRs are higher, indicating that the majority of patients referred to surgeons, require surgery. In contrast, when a traditional mix of doctors of all types (23%) or GPs (28%) refer, SCR are lower, indicating that a clear majority referrals do not result in surgery. Furthermore, pooled data for the more conservative measure of SCR, calculated using only data in which surgery was performed, suggest screening services (most often physiotherapy-led) may result in the highest SCR (Figure 3). Higher SCRs are considered desirable, ⁷ associated with increased productivity, efficiency and revenue, ⁸ better access for patients, potentially better outcomes for patients and reduced societal musculoskeletal economic burden. Consequently, these results suggest that contemporary musculoskeletal service delivery should include models of care that support allied-health/physiotherapy-led referrers and/or more specialised musculoskeletal doctors such as sports physicians.

Previously the SCR from physiotherapy-led screening services had been estimated with a wide range of 25% to 91% in a review of extended scope physiotherapy that retrieved 10 studies reporting SCR. ¹⁴ The present review updates and presents a much richer picture of SCR in physiotherapy-led screening services, including 18 studies reporting SCR for these services, in addition to synthesising the data with meta-analysis and comparing to other referrer types. A variety of factors other than the referrer have potential to impact orthopaedic SCR. Demand side factors may include patient choice and access to community musculoskeletal physiotherapy, while supply side factors may include waiting lists, and patient complexity. Screening services may include multidisciplinary allied health teams, providing a spectrum of physical and lifestyle options that provide patients additional choices in terms of physical activity, diet and psychological care that have been recommended for orthopaedic patients. ⁵¹ However, the impact of such interventions may take time to assimilate into a patient’s complex surgical decision-making framework, ⁵² highlighting the need for researchers and service providers to consider how surgery is measured within SCR calculations. It was beyond the scope of this review to examine all these factors. Past reviews into the impact and efficacy of physiotherapy-led triage or screening services have reported the success of these services and also suggested SCRs may be improved by these models of care.^11,12 The results of this review build on those findings, specifically in relation to SCR. Further research to determine the cost-effectiveness of different referral models is warranted and should include both the cost of referral pathways and the impact of efficiency variations within the surgical unit.

Heterogeneity (I ² ) scores were generally high, except in the case of no heterogeneity for sports physicians. As the intention of this review was to present observational data regarding the phenomenon of SCR, rather than trials of treatment effect, consideration of the sources of heterogeneity are more important than its calculated value. ⁵³ We have identified several key sources of heterogeneity, each of which are important to the understanding of SCR and have not previously been articulated as such in the literature. First is the methodology used to define a case as surgical (opinion, listed, had). Second is the type of referred condition; Table 1 highlights a wide range of conditions across studies. SCRs for different conditions have not previously been investigated and as most included studies did not present data specific to individual conditions, we were unable to undertake secondary analysis of this. Thirdly, the reason for the referral may vary for different studies. This is highlighted by contrasting an included study of 38 referrals specifically for arthroplasty in hip and knee osteoarthritis, ⁵⁴ with another included study of 362 mixed referrals for which the referral-reason was unknown. ⁴⁷ In the former relatively homogeneous cohort of hip and knee osteoarthritis patients, the SCR might reasonably be expected to be higher than in the latter cohort of mixed conditions, potentially referred for a variety of reasons including diagnostic uncertainty, funding rules etcetera, rather than with the expectation of surgery. Indeed, present understanding of the reasons behind orthopaedic referral represents another gap in the literature, as this has not previously been synthesised and was insufficiently described within included studies in this review, to permit even descriptive analysis. Finally, the professional autonomy of non-medical staff in allied health or physiotherapy-led screening services, creates another potential source of heterogeneity. The number of cases referred to surgeons is likely to be lower, and SCR higher, when allied health staff can autonomously access the necessary imaging and non-surgical care such as medicine prescription and corticosteroid injection. While the UK has made advances in these areas, ⁵⁵ internationally access for allied health staff lags behind. In models of care in which allied health staff are required to refer to surgeons to access investigations or non-surgical care (due to traditions or funding rules), SCR will be lower. As the first review to explore the methodological aspects of SCR, we believe these findings are both pertinent to observed pooled results in the present review and highlight methodological considerations for researchers. While the methodological quality of included studies was generally moderate to high, little consideration of the methods used to measure surgical status was encountered and future research into SCR should include details of the referral including the professional responsible, the reason for the referral and clearly articulate the method used to determine surgical cases.

This review has several strengths and limitations. A strength is presentation of the first review to explore the often-used metric of SCR in detail and present a meta-synthesis of data comparing different referrers. A limitation was the variable and often moderate methodological quality of included studies, however this likely had little impact on the primary review aim of reporting SCRs for different referrers. Due to the modest number of included studies and often small sample sizes within studies, numerical SCR calculations must be interpreted with caution. Furthermore, heterogeneity between studies and the discussed reasons behind this heterogeneity, simultaneously highlight the need to apply caution in generalising findings to all settings, yet also represent a strength of this review for being the first to highlight the importance of considering these methodological aspects in future research and service design. A final limitation was the that it was beyond the scope of this review to explore the numerous potential reasons underlying differences in SCR between referrer types. Further research is recommended to identify and quantify these differences.

Conclusion

Surgical conversion rates in musculoskeletal services vary according to the type of referrer. Lower SCRs result from traditional pathways in which all types of doctors or GPs refer patients, with higher SCRs achieved when referrals are received from physiotherapy-led screening services or sports physicians. Key methodological factors impacting SCR reporting include how cases are deemed surgical, the type of referred condition and the reasons for referral, all of which should be considered in future research. Findings suggest that musculoskeletal / orthopaedic services seeking efficiency through higher SCRs, should consider including sports physician or physiotherapy-led models of care for referral management.