Shanahan v Illawarra Retirement Trust [2025] NSWPIC 535

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Key takeaways

In this matter, the Personal Injury Commission (PIC) Member considered how Whole Person Impairment (WPI) should be aggregated where multiple injuries with different employers contributed to the same pathology (a back injury).

In determining whether an injury sustained in subsequent employment was a ‘new’ injury or an aggravation, the PIC relied on the common law principles of causation as set out in Oakley and Trustees of the Roman Catholic Church for the Diocese of Parramatta v Barnes (1990) 10 MVR 570 at 573 (Oakley).

Brief facts

The worker was employed by Illawarra Retirement Trust (IRT) when she suffered an injury to her back, which was deemed to have occurred on 16 January 2019.

The injury was first sustained on 29 September 2011, when the worker developed low back pain while cleaning a toilet during her employment with IRT. She experienced further flare-ups in August 2014, 2017 and 2018, and ultimately underwent surgery on 16 January 2019.

The worker sought an assessment of permanent impairment in 2020 and was assessed with 13% WPI. No claim for compensation was made at that time.

At the time of the 2020 assessment, the worker was working at a different employer as an in-home carer, having been terminated from IRT in July 2019. She later changed roles again in September 2021, reportedly without duties involving cleaning or repetitive bending.

The worker did not claim permanent impairment compensation until 2022. IRT had her assessed by Dr Bentivoglio, who assessed 14% WPI. On 18 January 2023, the worker signed a complying agreement for that assessment.

On 16 September 2022, while working for All Care Health Services Group Pty Ltd, the worker tripped and fell in a client’s driveway. She underwent further back surgery on 6 April 2023.

Her solicitors sought an updated assessment of permanent impairment from Dr Mastroianni, who assessed 17% WPI. He considered that the injury sustained on 16 September 2022 occurred against the background of the earlier injury in 2011, for which she had undergone surgery in January 2019.

The worker was later examined by a Medical Assessor who issued a Medical Assessment Certificate (MAC) on 31 July 2025, confirming the 17% WPI.

The worker sought a finding that her permanent impairment exceeded the threshold to claim work injury damages from IRT, her initial employer. She argued that IRT was responsible for the whole of the WPI she now suffered. IRT, on the other hand, contended that the 2022 injury was a new injury. This was the issue for determination.

Judgment

In considering if the worker’s permanent impairment exceeded the threshold to claim work injury damages (that is, whether IRT was responsible for the whole of the WPI she now suffered), Member McDonald considered the common law principles of causation as set out in Oakley.

In Oakley, three categories were identified in which the determination of causation required consideration of the effect of a subsequent injury on the cause of an earlier injury:

1. Where the further injury results from a subsequent accident which would not have occurred had the plaintiff not been in the physical condition caused by the defendant’s negligence, the added damage should be treated as caused by that negligence.
2. Where the further injury results from a subsequent accident, which would have occurred had the plaintiff been in normal health, but the damage sustained is greater because of aggravation of the earlier injury, the additional damage resulting from the aggravated injury should be treated as caused by the defendant’s negligence.
3. Where the further injury results from a subsequent accident which would have occurred had the plaintiff been in normal health, and the damage sustained includes no element of aggravation of the earlier injury, the subsequent accident and further injury should be regarded as causally independent of the first.

On the available evidence, Member McDonald considered that the 2022 injury fell into the second category in Oakley – that the further injury resulted from a subsequent accident, which would have occurred had the worker been in normal health, but the damage sustained was greater because of aggravation of the earlier injury. The Member found in accordance with the MAC (17%). It followed that the worker’s impairment exceeded the threshold of 15% to claim work injury damages.

Implications

The Member observed that neither the worker’s nor IRT’s medico-legal experts directly engaged with the categories set out in Oakley, and neither was asked a clear and concise set of questions.

In the context of WPI claims arising from an aggravation, it is imperative that letters of instruction to medico-legal experts include direct questions relating to subsequent injuries and whether the subsequent injury is a new injury or an aggravation, having reference to the principles outlined in Oakley.